But it's not that bad. You need to do research about your travel destination anyways, like how are you going to get around, what places you want to visit, and some basic phrases in the destination language if relevant. Spending an extra 2-3 minutes checking how much stuff you can bring and whether you need any "dark pattern" options shouldn't be too hard in comparison but maybe I expect too much of the average traveller.

I don't expect to have to research the bag sizes every time I fly to the same destination just because Ryanair might have made them ever so slightly smaller.

But they haven't. They only changed them once in the past decade, it's not like it's a thing that budget airlines pull every year. Changing them sucks but it's not really a problem now.