What’s Wrong With Illegal Immigrants?

Sorry if the title was a bit triggering. That’s not entirely unintentional, but the question is completely honest. I’m somewhat new to navigating the political world and would like to find a comfortable position before I feel obligated to vote again. I have heard the issue of immigration discussed quite often over the last few years and I’m curious where libertarians stand on the issue. In a broader sense, I’m also curious about the overall general consensus of the situation and where my personal thoughts are considered on the political spectrum.

What exactly is the problem with people coming to America from countries (primarily Mexico)? Even if they don’t do things the complete “legal” way? Is it simply an attachment to doing things specifically according to rule? Is it mostly just racism using legality as justification? Or is there some real sociological/economic loss that outweighs our moral obligation as humans? Personally, I feel like America is still the greatest country out there and I want everyone to come here so we can enjoy as much progress as possible. If that makes sense.

And I don’t mean to insult anyone who fully supports keeping immigrants out of the country. Just curious why it is even an issue and where do the various political groups fall on this subject.