Contrary to how this bill is usually portrayed in the news, this bill allows for using screws and gaskets. Those are enough to make a phone waterproof.
Lots of other waterproof equipment achieves Ip68 with only screws and gaskets. I don't see why phones should be any different.
You can still have a waterproof phone with replaceable battery through the revolutionary technology of gaskets ;-) There were several models like that already before manufacturers figured out it's cheaper to glue them
Price matters to consumers. If phones become more expensive because of this virtue signalling regulation it will be killed. The EU parliament is still a democracy.
What I would ask is that companies that create phones without replaceable batteries, should provide replacement by a reasonable fee (let's say no more than 9% the cost of the phone).
The problem that these bills are trying to solve isn't just consumer, it's End of Life management at the recycler level. Glued-in, Li-ion batteries over the years have caused so much headache for ewaste processors. Apple has improved over the years with their glue tabs, but it's still a big problem in the market as a whole.
You have that little confidence that engineers can make things waterproof? all it takes is a sealed environment with a gasket and a bunch of screws. Making "clip in" backs that are waterproof is a challenge, but there's no reason that has to be the norm, screws have worked for centuries and don't break nearly as often as clips
