I have some thoughts on this.
The Montero is the poor mans land cruiser. It was the top of the line SUV for Mitsubishi back in the day. They pulled out a lot of stops to make it shine in their line up and compete with other luxury SUVs. Because if that, Monteros are well/over built. They really are amazing trucks. However, because they are often cheaper than land cruisers or land rovers, they often get picked up for less, and then get taken care of less and abused more often. What I mean is, cutting corners on maintenance, neglecting basic care and just rough treatment over all. This makes any car unreliable. I’ve seen a lot of Monteros like this and they do seem to need a lot of work. I believe that this is why they get a bad rap from people about their reliability.
HOWEVER! If they are taken care of, they perform very well and last. Mine is very reliable, no major issues or things that are out of the ordinary. I bought mine from the PO who owned it for 100,000 miles and had every maintenance record for it since new.
From what I can gather, Monteros fair far better than a lot of American made trucks, and especially jeeps. But they are not as reliable as Toyota’s. I would say they come in 2nd behind Yotas. That being said, they do have their issues (depending on year and generation). I’m thinking of stuff like brake boosters, timing belt tensions, camber bolts seizing (gen 3). These can be big issues and a lot of Monteros suffer from the same kinds of issues, but at this point in their age, we have found most of the issues, people have dealt with them, and we have solutions that actually fix the issues. So that’s less of a problem and more of a speed bump.
So there is a bunch of thoughts on this. TLDR: Yes, I think they are reliable.