Fundamentally, the browser is the user's agent. Storing cookies, running tracking scripts, etc. should be controlled by the browser. Some browsers may take a strict "block everything" approach, some may be relaxed, and some may harass the user with prompts. Users are free to choose the appropriate browser.
Depending on websites to limit tracking by on their own is very difficult, since it is inherently against many websites' business model. They will keep trying to bypass the rules.
This is nice in theory, except the amount of fragmentation in 2020 is huge.
The average user simply cannot switch browsers.
The likelihood of encountering a website that breaks even switching from Chrome to Firefox is too much for any normal user to want to bother for just these purposes. They'll switch back the minute they find a website that doesn't work in their new browser, if they even get that far.
So unless you're suggesting "Chrome should make it more obvious how to clear cookies automatically and/or not accept them at all" (which seems like quite a UX challenge itself), saying "just tell everyone to switch browsers" just isn't going to work I don't think.
EDIT: to finish the thought -- yes I agree, browsers should provide users with choice, and switching browsers should be available to anyone who is unhappy with the way their browser treats their data, but that can't be the only way -- otherwise, the average user will get left behind.
I agree that switching browsers is too much to ask. But forcing websites to act against their own interests is not going to work either. It's like forcing a tiger to treat a deer with love and compassion. It's just unnatural. Do you seriously think Facebook is ever going to genuinely give users a way to opt out of tracking? Or Google? Never. They will always try to weasel out of all the requirements, always adhere to the letter but go against the spirit of these regulations.
At least browsers don't have that inherent agenda against their own users. There will always be a Firefox which genuinely strives to serve its users, rather than exploit them.
There is only so much that a browser can do.
It is fairly normal for some cookie values to be necessary for a website to function. Browsers should not be expected to differentiate these "necessary" values from values that support other features.
Browsers do provide these controls to users. You don't have to switch between them. More fine grained customization is possible with extensions, assuming you can trust extensions authors and the browser you're using supports them.
I remember reading a recent article claiming chrome tracks users even in incognito mode. I doubt those buttons to clear cookies and data do anything that hampers Google's ability to track you.
Depending on websites to limit tracking by on their own is very difficult, since it is inherently against many websites' business model. They will keep trying to bypass the rules.