My argument isn't realistic at all, what about people in third world countries who make good games but CAN'T afford that $100?
I can say the same thing for steam, however it comes down to how the platform is constructed and it's aim for users. Steam is a professional platform for quality games and thus from early on required users to pay to post a game, when it makes money, you get that money back.
However, itch has always been a open gate community that accepts everyone (if we ignore the nsfw ban and payment processor issue not long ago) so to suddenly gate keep itch with such force will push people away from a platform that was free. Because Steam is a platform users know that a huge chunk of games are paid titles, whereas, people come to itch because of the amount of free to play games and easy methods to support small devs via buying their demo or donating.. and if you suddenly add a payment to post a game.. you can say goodbye to most if not all the free to play game.. as paying to post your own game free or not will completely flip itch's devs and users on their heads.
Paying $100 to post your game on a platform originally designed and pointed for new devs with required $0 upfront cost is pretty extreme.
A far better direction would be for itch to hire more staff or use their current staff to tighten up rules and regulations on the platform that DOESN'T require a complete restructure that makes their users and creators suffer entirely. Such as implementing better and improved upload rules for games, holding games for review if enough people report the game and, ensuring people follow.
I do agree that itch has become a place full off ranged levels of effort in terms of game quality, however itch has been built on "open for all" and "fair chance for all" and as such, in order to somewhat keep that going and be fair on everyone, they need to tighten the rules on the quality of game you can upload and add a few new rules.
What you are suggesting is "Welcome to my restaurant that anyone can enter, but you must pay us $100 to eat here" But the restaurant in question is McDonalds, not some fancy club restaurant.