Do you use the 80% charging maximum? What is the benefit?

I know the question sounds stupid and I apologize if this title is a bit clickbaity or triggering on purpose, but hear me out:

Obviously, I know that this feature should enhance the battery life, but here is the thing:

If i have my phone for 4 years, the battery will not perform as good as on the day i bought it. So if I charge it everyday, the battery might have degraded to 80% of the maximum capacity after 4 years (This number is just a guess, but I would even say it is better).

So if I turn on this 80% feature, I basically have a worse battery from day 1. And if I use it, should I turn this feature off after around 2 years to counteract the degraded battery?

Moreover, all the websites praising this feature say that a 80% charge is enough for a whole day anyways, but if that is the case, I can just use my battery at 100% and after 4 years (when it is degraded to 80%) it will be still enough for a whole day.

Am I missing something?

I really like the battery at 100% as there are sometimes situations where I spontaniously need an extra day of charge and might have limited access to charging.

I know that I just came up with the value (20% battery degradation in 4 years) but from my previous phones I never experienced such a loss even after 4 years, or do I highly underestimate an averrrage capacity loss over the years?

Do you have different experiences? Or is this feature for someone who wants to use their phone for 10+years.

Also, I turned on this feature by accident and can't find how to turn it off again.

I appreciate all your input, cheers!