Not worth doing up for any use other than as a commuter.
26" wheels are obsolete
it was a cheap bike with a budget groupset and rubbish fork. Better of buying something newer secondhand or new if you want a gravel or mountain bike.
Ya not worth it. As an owner of a 90’s Schwinn Tomato hard tail that I used to race, just finding parts is hard. If you do find race parts they are expensive. While still fun to ride while on a camping trip, not near as fast as a newer full suspension bike.
This. Like others have said, 26" mountain bikes are obsolete, and you’ll have trouble finding new parts. (I had the same issue with my 2012 26" fully, it was the last of its 26" breed, and it wasn’t financially sensible to restore it.)
I’d only fix it up if you like doing that sort of thing and you find it therapeutic.
It’s not so much the 26" tires that make this bike not really worth restoring. It’s more that the bike wasn’t a great bike in the first place (it wasn’t junk, but it was pretty basic). It would make a good cheap commuter, but I’d only do tires/tubes and cables, not a full restoration - keep it cheap and use as a true beater bike that you don’t care if it gets stolen.
Some old 26" mountain bikes are worth restoring for nostalgia’s sake (think vintage Kleins and FatChance, etc).
Some make decent gravel/all-road bikes (mid-90s Stumpjumpers come to mind). Maybe with flared drops, maybe adding a rigid fork (vs rebuilding an outdated suspension fork).
And some make fun basket bike/pub cruisers. My 1983 Stumpjumper falls in this category.
(but I wouldn’t restore an old 26" bike for actual trail use - as noted, for similar money, you can get a much newer but used 29er that will outperform the 26" in every way)
A few years ago I did this with my late-90s Orange Clockwork. I sourced some PACE suspension forks on eBay, and some other period pieces like a USE stem and Onza bar-ends, and gave it all to my LBS to refurbish. It didn’t cost all that much. It’s not that nice to ride off-road - the forks have such little travel - but it’s great for riding with my small son and running errands, and I’d rather it had some use than just sit idle.
The selection of 26 or 27.5x 38-40c tires just isn’t there. The 4300 was the very basic model too - that’s a lesser version of a current $600 Trek Marlin 5. That bike is also just the wrong fit for you.
By the time you buy 2x tires and tubes ($120) , bars ($30)/ tape ($20)/ levers ($50), cables ($40), chain ($30) etc etc etc you’re gonna eat up a lot of money that could be spent on a $1100 new Giant Contend AR/Revolt/escape disc, Trek Domane/Checkpoint, Salsa Journeyman, Canyon Grizl, specialized sirris x/diverge etc that you’ll be much happier with. Probably even the Marlin out of the box would be a better buy than them your converse bike.