Of course you can. But if you know a little bit about how religion works then you will realize that it is strongly coupled to the identity of the person. Someone isn't a carpenter or a baker in the same way that they are Hindu, Muslim, Christian or Jew. They can't just turn off that chunk of their identity while you question their religious values or their religion, they will interpret it as an attack on
them. And that's half the problem.
The other half is that any religion - and therefore most of its adherents - are conservative and static. They would like things to stay the way they are. Obviously this is at extreme odds with emigrating from one place into another. People not only bring their culture with them but also some of their luggage. But the locals would do well to realize that they too are usually not exactly paragons of virtue and that there are plenty of things where they would feel personally offended if an outsider pointed out to them that they were maybe not all that level headed about something.
For instance: in NL we have this crazy confrontation about St. Nicholas, which arguably is a racist display in the guise of a childrens festival. Or maybe it really is just a childrens festival. Everybody has an opinion and it is always either the one or the other but never anything with some nuance. So fights break out and everybody feels like they are the ones in the right.
That's what identity will do for you.
If you want to question religious values and religions themselves then you're going to have to start by planning something that will take decades. It took some small parts of 'the West' about 100 years to go from majority strongly Catholic or other Christian denominations to being more accepting of atheists and that in turn led to those places eventually losing a lot of religion. And that's with a religion that went through the enlightenment, which isn't the case for most religions practiced outside of Europe, and only then because the main centers for religion in Europe all were subject to this (and to the horrors that came before).
So in a way all this feels like a step back. But fixing it will take at least 100 years and probably more. Without an actual solution in the form of education, massive funding and housing and healthcare improved at a scale that no country in the West could afford based on their present day budget it may well never be solved at all.
As for whether or not I'd be suspicious of a person who belongs to a cult, my grandmother belonged to the cult of Catholicism, and we didn't see eye to eye on a great many subjects. But I didn't have a problem with it, she was my grandmother. Neighbors are practicing Muslims, I don't have any problem with that, it's their heads and their houses.
And then we come to your 2.
If you move to a country I think your first and foremost pledge should be that you are not going to put your past to work to recreate the place that you fled from in the place that you've arrived at. But people are hardly aware that this is what they are doing, they are so immersed in this that it is invisible to them. And that's a serious problem that I think will only be solved in many generations, and possibly never.
You can probably sense that I don't have a high regard for religion, not because I don't think people should not be able to believe whatever they want to believe but because it brings so much misery. I've seen plenty of this up close to know that most of the people that do this do it from the conviction that they - and not you or I - are in the right. And that's a very difficult thing to repair because then we're back at identity again.