I have a 1977 Raleigh Competition GS, if I wanted to, I could easily trust this bike to do a credit card tour across the USA with minimal problems other than standard maintenance!
I have a low end 1997 Giant Rincon with XT derailleurs which were not supposed to be on the bike new but that's the way it came from the factory. Anyway, those XT components are junk, I've taken it to several bike shops and they can't figure it out, internet said that era of XT had a lot of issues, that bike I would not trust riding across the USA unless I put on new derailleurs. The first era of clutch XT derailleurs were also problematic. I bashed that bike around quite a bit, but the derailleur issue was something it always did, I just rode it in spite of the problem.
Whether or not you can trust an older bike depends entirely on how well it has been maintained and how good the components are. All my bikes, from 77 on up I would trust to ride across the US except for the current condition Giant.
If that Scott has been lightly used, it should have no problems riding it off-road, at least till you put some miles of bashing on it. But keep it maintained and it could last a long time.