Over the past decade, Amazon (NASDAQ:AMZN) has expanded its portfolio of private-label goods, which now include batteries, diapers, packaged foods, apparel, toys, mattresses, and more. Many analysts believe that expansion could eventually harm a wide range of companies and tighten Amazon's grip on consumers.

SunTrust Robinson Humphrey, for example, expects Amazon's private-label revenue to rise from $7.5 billion in 2019 to $25 billion in 2022. TJI Research estimates that Amazon now sells over 550 types of private-label or exclusive third-party products on its marketplace, and many of those products were only introduced within the past two years.

This sounds like dire news for retailers, but a recent Marketplace Pulse study of 23,000 products found that shoppers actually weren't inclined to buy Amazon's private-label products -- even when the company promoted them above third-party products in its search results.

Marketplace Pulse founder Juozas Kaziukenas claims that the notion that Amazon can "introduce a product and magically use data to dominate a category is just a conspiracy theory." Kaziukenas claims that analysts cite a few successful examples, like batteries, to support that narrative, but most of Amazon's other products "aren't successful at all," and other companies "continue to outsell" Amazon's private-label products.

Check out the latest earnings call transcript for Amazon.

Did the "Death Star" miss its target?

Amazon's introduction of private-label products isn't a novel idea. Plenty of other major retailers, like Walmart and Kroger, already sell many private-label brands.

However, Amazon's aggressive expansion of its private-label brands spooked many retailers since its online marketplace disrupted many brick-and-mortar businesses. Moreover, Amazon's expansion of its Prime ecosystem, its acquisition of Whole Foods, and its other brick-and-mortar efforts indicated that it could wage prolonged wars against retailers on multiple fronts.

Yet Wall Street analysts, many of whom dubbed Amazon the "Death Star" of retail, often overestimate the e-commerce giant's ability to disrupt other markets. Analysts once claimed that Amazon could kill Etsy with its Handmade marketplace, Grubhub with its food-delivery services, Groupon with Amazon Local, and Expedia with online travel services.

Amazon didn't disrupt any of those markets, but the idea that it could still "kill" companies by expanding into adjacent markets remains popular. Therefore, it isn't surprising that some analysts jumped the gun and declared that Amazon's private-label brands could punish brick-and-mortar retailers.

Commodity items vs. brand-name goods

Marketplace Pulse's study isn't a definitive verdict on Amazon's private-label efforts, but it indicates that the company could be struggling to build its brands.

Amazon sells about 5,000 private-label clothing items, according to Coresight Research, but it doesn't heavily promote these brands with major ad campaigns. Therefore, it's unclear why average customers would buy Amazon's "Core 10" yoga pants instead of similar products from Lululemon, its "Peak Velocity" activewear instead of Nike activewear, and so on.

The apparel market is already notoriously tough for established retailers thanks to fickle shopping habits and competition from fast-fashion rivals, so it could be tough for Amazon to establish any recognition for its private-label brands. The same can be said about other products that are dominated by market-leading brands.

On the bright side, Amazon should keep performing well in commoditized markets like batteries, USB cables, and power strips -- since customers generally buy the cheapest version of those products instead of staying loyal to a single brand.

The bottom line

Amazon's online marketplaces generated 13% annual sales growth last quarter, so it's still locking in plenty of customers. However, it's also running out of room to grow in mature markets like the United States, where it already controls nearly half of the e-commerce market, and launching more private-label brands could help it squeeze out more profit per customer.

Amazon's expansion of its private-label brands is still a smart long-term move, but investors shouldn't assume that the "Death Star" can obliterate everything in its path. Instead, Amazon's private-label business should keep flourishing in certain commoditized markets, but struggle to pull shoppers away from established brands.