Many Catholics believe in the tooth fairy. Somehow, I don’t think that makes it real.
Pretty much anybody can get a nice shirt and a nice pair of pants to wear to church. And in fact, most of the really poor people who attend church will dress up in their best, every Sunday. They have pride.
If someone genuinely doesn’t have any clothing but what they’re standing up in, then yes, the Church should welcome him, whatever the tatters or smells. Then the Church should make sure to provide this person with nice clean clothes, hygiene help, and whatever else he may need.
But usually, the people I see dressing insufficiently have vast wardrobes. The richer the person is, the less likely they are to dress up for Mass (or have sidewalks clear of snow in the winter. Not an absolute rule, but pretty close).
Nobody is saying anybody should be tossed out, but people should have some rudimentary idea that Mass is the most important thing you attend all week.