Assuming you're asking about things like impossible and beyond meat. They are generally not "healthy" but one stark difference is they don't have cholesterol.
Whether something is healthy or not is very contentious in the first place, especially with how much misinformation there is out there.
I just try to read the labels on the replacements I buy, and most of them just have many random vegetables and stuff, with a seemingly good balance in nutrients and so on. Maybe there is stuff I'm missing, but I don't see much bad that can be in there.
I think the most important thing is to just have a relatively balanced diet.
I'd say that they are as healthy as the burger king meat they are substituting. I wouldn't eat either but if you are there, picking either is equally bad so whatever.
The unhealthiest part about them is just gonna be that they're salty, fried and greasy, just like other fast food. It's just a lump of plant fibres (usually peas or wheat these days, I find) thrown in a frier.
I assure you these people are not eating healthy meals lol, it's all bad faith because the idea of them not eating meat makes them feel threatened about the size of their peepee.