some people don't know that, and it isn't made obvious, so having it by default on is great i think... but, enabling it at random for no reason? that's ridiculous
if i get some spare time i'll throw some rounded corners on some of my recent web designs that i'm allowed to show, though i've thought about it more and i don't think that's my main issue with it. i feel it makes it feel like websites are more so just that, little pages in an app, when they can be, and often times are, so much more. i like when they can take their whole screen of space, without any borders, cut edges, anything like that, which is why i personally use a theme which even hides the tab bar behind a hover. i like to treat websites as apps in their own right, and putting them into a little box just doesn't sit right with me. if it didnt have those borders, and were just rounded based on the normal windows border radius, i'd likely be fine, but i feel this puts too much connection between the browser and the site
i've designed a few websites recently which really favour sharp corners, and when one of my sharp objects randomly has a rounded corner, when none of the others do, just because it happens to be in the top left corner, in my opinion that's a bad thing?
if you're on windows it cant really theme that well, but if you're on linux you can use qt6ct to retheme it to look a bit newer, i'm using the "kvantum-dark" theme
some people don't know that, and it isn't made obvious, so having it by default on is great i think... but, enabling it at random for no reason? that's ridiculous