The problem is the lack of diversity. Google controls Chromium and almost all browsers are Chromium based so Google controlls the supported web features of almost all browsers, giving them the power to decide which web features are supported on the internet and which aren't. They use this for example to push their own file formats for the web instead of better alternatlives. Remember when everyone was mad that ublock origin wouldn't work on Chromium browsers anymore? Same thing. They get money from ads so they make it harder to block them. Google shouldn't have that much power over the web.