Shares of “The Big Bang Theory” network CBS plummeted Wednesday as Wall Street digested its planned merger with Viacom and decided the benefits of the merger are too little too late.

Bernstein analyst Todd Juenger cast the deal — aimed at creating a media conglomerate to compete with the likes of Netflix and Disney — as a copycat move that lacks sufficient scale to succeed.

“We don’t think it’s too much of a stretch to say that CBS/Viacom, like many others, has seen the stock market’s positive reaction to Disney’s plans and decided ‘let’s do that too,’ ” he wrote in an update that lowered CBS’ rating to underperform.

Juenger’s reaction, coupled with other negative reviews, sent the stocks of Viacom and CBS down 8.5% and 8.3%, respectively — almost three times the Dow’s plunge on Wednesday of 3.1%.

BMO analyst Daniel Salmon also downgraded CBS’ stock to market perform, claiming “the next 12 months are more likely to be focused on near-term content investment and potentially more M&A.”

Macquarie’s analysts stayed neutral on CBS. But they downgraded Viacom to neutral on grounds that its stock, which used to command a premium, will “now track CBS shares on the established exchange ratio.”

Even watchers who agreed that the merger makes sense said it’s coming too late to compete with the likes of Disney, which announced on Aug. 6 that it would bundle its Disney+, Hulu and ESPN+ brands for just $13 a month.

CBS currently charges about $15 a month for for its streaming offerings — CBS All Access and Showtime All Access — Juenger said in his update.

“We see no way that $15 bundle would work with consumers,” he said, noting that Netflix’s core plan, like Disney’s bundle, also comes in around $13 a month.

Merrill Lynch’s Jessica Reif Ehrlich was more charitable. She upgraded CBS and said the deal promises $500 million in synergies, greater scale in content production and “enhanced negotiating leverage” during negotiations over programming fees.

CFRA analyst Tuna Amobi was also upbeat that after years of on-and-off, at times rancorous, discussions, the companies will now try to “unlock value together.”

“It won’t be an overnight hit, but there’s a compelling case long term,” he told The Post.