Some people think they are frum.
Some people dress like frum.
You will find the ones who are particular and strict are the least frum in the reckoning.
As the Chofetz Chaim says: the malachim judge you the way you judge others. If you are particular and hard with others, they will be the same to you. And since those sorts of frum people don’t seem to know that, more fool them.
Who knows whether Eliyahu Hanavi or Yaakov Aveinu is one of those hatless people in shule?
And yeah, I don’t wear a hat when praying. Who cares. What matters is speech and subduing anger – hat is a pale comparison. Ha.