[Closed] Is it worth upgrading an old bike?

Lurking at the back of my garage is an early 90s steel HT Marin which is used as a hack bike. Recently I had been fancying a steel hardtail to complement the FS bike. Am I better off buying a new frame or could I mkae a decent bike out of the Marin. I have some odds and ends to start a build, disc wheels, forks etc so all the marin would need that is different would be a rear disc adaptor. Do people think I would be disappointed with a pimped 90s bike or would it do the job enjoyably--long peaks rides mainly.?