Wow, I’m in exactly the same situation. Moved to UK (London) two years back in my 40s. Took a 15% pay cut for the same role/company. Pandemic happened, didn’t love 8 months of dull grey weather & 4 months of sun, found a job in the US and moved back.
Now I miss it and moving back next month! I like the ‘quality of life’ way better. That’s a phrase that means different things to different people. I don’t have kids, which is a huge factor. If you’ve saved well early in your career in the US, moving to Europe could be a win win.
Yes the tax filings are a pain. Everything works less professionally overall - you have to “chase” people to get work done (a word used a lot in the UK) and the grey weather can get to you, but I’m going to give it another chance.
NHS is ok, but be aware there isn’t a whole lot in term of preventive care. Private health insurance even through an employer will not cover chronic preexisting conditions (diabetes, heart disease, etc.), unlike in the US - something to consider if it matters, though private hospital bills won’t bankrupt you either unlike the US.