I would rather have a modern mountain bike personally if I am mountain biking but as a vintage bike they can be quite nice. Anything Ti has me excited. If it has decent parts XT/XTR it is likely to be a pretty good bike as Marin had a decent reputation. I would say any of the early Full Suspension stuff like ether F.R.S. would be silly but not a bad bike just poor early ideas for suspension that helped a little but sometimes were harsh and are certainly a pain to deal with 30 years later.

Depending on what you are doing, go for it but I will say if I was going Marin, the modern Pine Mountain 2 looked to be a pretty neat bike for off-road adventures. I built up a vintage MTB and realized I didn't love it as much as my modern bikes and it wasn't a bad bike, loads of great parts from Paul and Shimano and it was a lovely ti frame it just wasn't what I wanted for MTB and in that build it wasn't what I wanted as a gravel bike but I may rebuild the frame at some point and make it cool.