It's like a factory that dumped toxic waste into a river complaining that, because of a ban on dumping toxic waste into rivers, they now "have to" dump them to nearby meadows instead, and that makes local customers unhappy.
"Detrimental effect on user experience" is an intended effect that clearly signals the company doesn't want to stop abusing its users.
Every business: "Stuff in here causes cancer."
Every customer: "Okay."
Every customer: "OK."
They're not required to unless they're using cookies for something other than providing better experience. Also, that's cookie laws, not GDPR.
It's more like:
GDPR: "We see you doing X, Y and Z which are pretty abusive. We want you to not do X, Y and Z, but if you absolutely must, you can only do that to volunteers and you can't deny service to people who do not volunteer. Oh, and it really must be opt-in."
Every business: "Hey, we do X, Y and Z. That okay? [x] no >>> [ ] <<< !! YES PRETTY PLEASE".
GDPR is a massive win for the individual.
Cookies are a separate law and entirely unrelated to GDPR.
Also the annoying "this is what we are doing, you have to agree to this to proceed" is explicitly forbidden for the GDPR. So your criticism does not apply.
The status quo where corporations make vast profits peddling ever finer-grained user data unbeknownst to the consumer with no oversight is not good. A cultural shift is necessary. I'm glad to see the EU has the stones to tackle the issue because there is zero political will stateside for any political action other than driving corporate profits masked by populist appeals to xenophobia and whatever other irrelevant distractions they can cook up.