What do you mean "nothing has changed"? Using your numbers, the SNR went off a cliff.
Use HN as an example - I used read the new stories all the time before they hit the frontpage, and upvote as needed.
But with 100s of slop submitted for every 1 actual good article, I can't do that anymore.
IOW, I have finite time. If 10% of the population is now able to vomit out side-projects, I am never going to find the one good one because it will be lost in a sea of rubbish.
And you're right that people still have limited, fixed bandwidth with regards to attention available to give to things.. and the same amount of things that break through doesn't change from what could break through and stick before (in the monoculture). But the amount of niches/verticals where you have the opportunity to break through inside of is significantly higher than ever. That gives you a better chance for success, because your audience is more targeted, more receptive, hungrier for authenticity, hungrier for quality, and desperate for connection to something they like.
TL;DR if you have a good, valuable idea that people want (or don't yet know that they want), execute it well, deliver something that is undeniable, promote it effectively, and stick it out for the long haul, you'll find success. There's no magic formula beyond that, and it doesn't matter if there are 10 or 10 million amateurs clogging the toilet bowl next to you.