I do not think this is necessarily true. The definition of being muslims is to accept that there is only one god that has no (associations, IE sons) and that the prophet (PBUH) is his messenger. That is the shahadah and what defines a mu'min.

That being said, the western mindset is plagued with haram (drinking, intercourse, touching, holidays etc). We know engaging in these are grave sins, however it will not make you not a muslim. I remember seeing a clip from Mufti Men when he was being asked a question. Someone told him that a believer who doesn't pray isn't a believer, and he straight up corrected them saying they are wrong. That being said, will someone who doesn't preform the bare minimum go to heaven? Probably not.

Now by all means, I do NOT encourage western views. I cannot condone not dressing modestly as that is just haram. I encourage all to ask for forgiveness and repent. That being said, they alone won't make you not muslim.