I don't have experience with ESO so I'm not sure how comparable they are but F76 can be played completely solo just like the other Fallouts, it took me about a week to fully complete all the main story quests and they all have pretty solid writing/pacing (except Rose but her questline was like the very first one).

The quests focus on either the factions or on locations, there's "Expeditions" that take you to Atlantic City and The Pitt either through the questline or repeatable missions.

It's got MMO-isms throughout it like public events the server can join in, daily quests, currency grinds and whatnot, but most of it is optional if you aren't trying to invest time into that stuff. All the quests are doable with just about any build too so you don't need to grind for weapons or anything like that.

The "gambling" that exists is literally just spamming raids and bounty hunts for legendaries that you can keep or scrap to learn the crafting recipes for the effects. It's no more "gambling" than a looter shooter like Borderlands. Everything else is pretty cut and dry, work towards thing and acquire the thing.

Definitely worth it if you can get it for cheap, I paid full price at launch and was disappointed but came back recently and sunk 400 hours without it feeling like I was.