I've seen this sentiment before, but I don't get it. Sure, the internet's mainstream and there are parts of it that have a mainstream culture and that's probably not going anywhere in the foreseeable future.
But the internet itself has no culture (heh). It's just a network. There are still corners of the internet that have whatever culture you're looking for. And if you can't find it, you can make it. It probably won't make much money or make the news, but the option is there.
That said, I agree with the main thrust of your argument that tech companies are just reflecting the mainstream preference to whitewash reality.
I am well aware that niche chasing is the way to achieve it for now. What the sentiment longs for as ideal is for influence to have worked more in the opposite direction. Instead we get advertisers trying to be the tail wagging the dog again when people left their last venture over the blandness they imposed.