Yet I get the feeling that younger Poles don't feel it so much
You're getting this feeling based on what?
many young Poles don't regard themselves so much as Poles but more as Europeans
I really doubt that's the case with majority of young Poles.
I do worry that some younger Poles are becoming less patriotic.
What do you mean by "younger Poles" and "becoming less patriotic"? Less patriotic than Poles older than them or than young people in the past?
According to this poll from 2021 majority of Poles in every age group consider themselves to be patriots: