I feel like you've made a lot of assertions that don't make a lot of sense when compared to the real world. I agree that WotC is nothing like they used to be, have been gutted by Hasbro, and 5e is a pretty stale and lame example of a TTRPG. That doesn't make it any less easy to learn or homebrew. The starter sets and basic adventures were simple enough for my mother, a teacher, who has absolutely no TTRPG experience, to run a game with her 5th grade students, who were perfectly capable of handling the premade characters and simple module. The game has a very easy entry point, and even when approaching the full ruleset, isn't hard to understand when actually reading the books (especially the new ones, all their other major flaws aside), which more people do than you're suggesting. New players get excited, the PHB is easy enough to follow with interesting art and ideas, and you really don't even need the DMG to run a successful game, though the frameworks it sets up can make your life easier.

There is a reason other than branding that DnD remains as incredibly popular as it is, as no matter how many streamers play it and how much sponsorship money DnD beyond gives out, if new players enticed to try the game couldn't get the hang of it pretty quickly, they wouldn't stick around. Are there better systems for modularity and ease of play? Obviously. But that doesn't make those things untrue for 5e. The million Kickstarter projects with homebrew should be examples enough. You keep asserting that "no one plays 5e as designed," which is technically true if you define that as only using rules strictly in the books, but really misses the point. People are using the classes and mechanics put into the game, and a great deal of official optional rules have become ubiquitous in every game. Popular house rules get added on, and people make up their own mechanics, because it's a TTRPG, and that's true for any of them.

Obviously there aren't great sources that aren't anecdotal, but a quick glance around LFG posts, LGS events, and online DnD specific communities should be enough to show that people are indeed playing the game "as intended," and home brewing to their heart's content. The reputation you claim 5e has simply doesn't exist to the casual player. You're totally right, in that this is how most dedicated TTRPG communities see the game, but to the casual player (which is most of them), 5e is what the cool streamers play. They watch it, think "Hm, that doesn't look so hard," grab a book and run with it. I've seen this happen repeatedly with friends that have never played a TTRPG in their life. They don't know about WotC's past, they don't know about the company being gutted, and they don't know about the designers abandoning a lost cause. All they know DnD as is the default TTRPG (which it shouldn't be), and pick it up, finding it easy enough to play and homebrew.