My daily driver is a 90's bike, so I understand.

But ... while this is a very good 90's bike, I really don't think it's a "MTB", not even by 90's standards. A 90's MTB would have much more aggressive tires and probably front suspension. Honestly, this looks more like a 'gravel bike' to me (sans your cargo upgrades). If 'gravel bikes' were even a thing in the 90's. (That said, if you're taking it on trails like the one pictured and want to call it a MTB ... then it's a MTB. IMO, bike classifications should ultimately be determined by how you actually use it. You could have today's best and most aggressive downhill MTB, but if you only ever ride it on suburban streets and sidewalks, then that makes it a cruiser, not a MTB.)

And ... yeah. For cruiser/street/commuting bikes, I think 90's bikes are fine. That's why I use one. But actual mountain bikes have come a long way since the 90s. My mountain bike is a much more modern bike with 29's, full suspension, and disk brakes ... and those upgrades make a world of difference, even at the cheap end of the spectrum, which mine very much is, at $200 brand new. Not just more comfortable, but also a lot safer (mainly due to much better brakes) and able to make it through more difficult obstacles without dismounting.