The joy of the January revolution of 2011 has given way to the return of a form of authoritarian rule. How much power does the country's new strongman, Abdel Fatah al-Sisi, intend to wield?

The activist Alaa Abd El Fattah is one of at least 16,000 political dissidents languishing in an Egyptian jail and it was from his cell that he wrote the following last week: "Everyone knows that most of those in jail are young, and that oppression is targeting an entire generation to subjugate it to a regime that understands how separate it is from them and that does not want to, and cannot in any case, accommodate or include them."

It is a bleak assessment of contemporary Egypt, three years and two months after a revolution that was supposed to empower Abd El Fattah and many of those in jail with him. In his letter Abd El Fattah highlights the arbitrary nature of many of their detentions, the torture to which thousands have probably been subjected – and the apathy towards, and often enthusiasm for, such malpractice among the public.

Among Egypt's revolutionaries and rights lawyers, it is no longer remarkable to say the country has returned to the era of Hosni Mubarak – or worse. To Abd El Fattah's portrait of a revolution turned on its head, others might add, among many other criticisms: untrammelled police brutality; journalists jailed; a ban on the kind of protests that drove the 2011 uprising; the exile of Mohamed ElBaradei and Wael Ghonim, two of the politicians and activists most associated with Mubarak's downfall. Plus the likely election to the presidency of the army chief whose presence has come hand in hand with the restoration of Mubarak-style oppression: Abdel Fatah al-Sisi.

In cabinet, writes one former minister under Mohamed Morsi, whose year-long presidency was toppled last July, "there is now no one left that has any link to the 25 January revolution". The nuance of Yahia Hamed's point is debatable, not least because Morsi's own government had autocratic leanings, and the extent to which Morsi's Muslim Brotherhood was involved at the start of the 2011 uprising has long been contested. But Hamed's general premise stands: Egypt's recent cabinet reshuffle saw the departure of the most moderate voices in government – the secular liberals who supported Morsi's overthrow last July, not because they craved greater authoritarianism but because they wanted less of it.

But to what extent all this marks a full-circle return to permanent dictatorship – and how similar such a dictatorship would be to Mubarak's – is open to question. It is sometimes assumed that Sisi's grip on power is total. Certainly he enjoys more influence than any other Egyptian and has a large, sycophantic following. But how much power he wields directly – and how much cohesion there is between his army, the secret police, the cabinet, and the judiciary – is unknown.

"For me, the most outstanding feature of this moment is that nobody is in charge," says Michael Hanna, an analyst of Egyptian politics. "The military is not really in charge and it's not making systemic decisions." Even if Sisi is in favour of it, the thinking goes, he might not be directly co-ordinating Egypt's oppression – which may instead be the result of different factions elsewhere in the state using a vacuum in leadership to assert themselves. "So the real test comes post-election," says Hanna.

"Will a President Sisi – with the backing of the military, and with what he would consider a popular mandate – then decide he can make decisions?"

However he acts, it should also not be assumed that Sisi represents quite the same elites as Mubarak did. Sisi may have been head of army intelligence under the ousted dictator, and Egypt's latest prime minister may hail from Mubarak's National Democratic party (NDP). But in Mubarak's last years, senior army officials were at loggerheads with the NDP leadership, whose neo-liberal instincts threatened the military's vast economic empire. When Mubarak fell, leaving senior generals in charge, it was those NDP officials – including Mubarak's son Gamal – who were among the first to experience retribution.

"The NDP neglected society," says one senior officer, who was keen to portray the army as Egypt's salvation. "Their corruption is the reason people are still suffering. They will never come back and the Mubarak era will never come back. A new era is coming."

As Abd El Fattah's prison letter shows, many fear this new era will nevertheless bear many of the oppressive hallmarks of the old one. But others also maintain that the country's dire economic predicament will not allow any new government to use violence to crush dissent indefinitely. As an increasing range of workers' strikes show, officials have nothing to offer the public in exchange for the removal of their political rights. And even if the immediate outlook is dark, this argument continues, the residue of revolutionary gains will remain.

"I don't think you can roll back the gains of liberal principles in the last few years," summarises Samir Radwan, Egypt's first finance minister of the post-Mubarak era, who believes the country's civil society is still in much better shape than it was four years ago.

Hala Shukrallah, who became Egypt's first female leader of a political party earlier this month, is a case in point. Her rise is one scarcely imaginable four years ago – a reflection, she told the Observer, of "real, deep changes in the psyche of the Egyptian people and the Egyptian youth".

Likewise, several activists were arrested for campaigning against Egypt's latest constitution, which passed in January. But the text itself, though flawed, represented a small incremental gain: it is comparatively more liberal than any predecessors.

Detainees enter police custody expecting to be beaten and tortured – but it has not all been one-way traffic. To the surprise of many, the policemen who murdered Khaled Said in 2010 – the attack was one of the rallying points for the 2011 revolution – had their sentences extended last month. A police captain, culpable for the gassing to death of 37 prisoners inside a prison van last August, was jailed for 10 years last week. These are extremely rare convictions, and farcically lenient in comparison to the sentences some Morsi supporters have been given simply for protesting. But at a time of seemingly unstoppable police influence, two judges have still been independent enough to convict serving officers.

It was intriguing, too, to see the face of Hisham Geneina peering from an Egyptian broadsheet last week. Geneina, Egypt's chief auditor, had given an interview criticising the police for obstructing his employees' post-audit of their accounts – and he later expanded on his allegations to the Observer. The accountants who did the police's pre-audit, Geneina said, were paid by the police – which, he argued, caused an obvious conflict of interest. Meanwhile, Geneina's team on the post-audit were sometimes not given the paper records they needed. It was not the most rebellious outburst but, given the political climate, it was also not the most compliant.

But for the thousands in prison, or the young Islamists growing frustrated with the futility of street protests, a few hints of optimism here and there mean little amid a wider environment of wholesale oppression. In his letter from prison, Alaa Abd El Fattah argues that Egyptians have allowed themselves to become deceived by a bogus promise of gradual progress and the "show" of democratic process.

"The show helps to normalise the situation," Abd El Fattah writes, "it [diverts people] on to useless routes: negotiations, advice, legal representations, efforts with the media – until the common understanding becomes that anyone who's accused is guilty, that it's up to the revolutionaries to avoid being imprisoned or killed."

He ends with a rousing call to action: "Everyone knows there is no hope for us who have gone ahead into prison, except through you who will surely follow. So what are you going to do?"

The success of Egypt's next president may depend on the response.