Poles I met would actually claim they had no accent.
I've come across this too, as well as Poles who expect to learn to speak what they think is accentless English (this usually means what used to be called a BBC accent). In reality, they're confusing pronunciation with accent.
One issue for Polish speakers of English is pronouncing the / ɔ: / phoneme and to a lesser extent / ɜː / and / ə /. It's actually quite hard to teach and is probably harder to deal with in the class room than / θ and / ð /. Generally / ŋ / is easy since there's a near equivalent in Polish, though not an obvious one to non-specialists and I doubt whether most of the people in private language schools cotton on to this.
I don't need to "analyze" accents anymore
You just said that you had. perhaps you should make your mind up or better still, show restraint about posting low quality stuff for the sake of it.
And this topic is about teaching in Poland, not your bile about non-standard forms of English or your personal history.