I've spent the last year or so playing Tom Clancy's Ghost Recon Breakpoint with a couple friends.

It has an interesting sci-fi/military story, tons of side missions if you're tired of following the main campaign, and a wide open map to explore if you're just bored of everything. Plus, there are random missions every day, so if you're done with the main campaign, you can continue to do missions and enjoy exploring the world even more.

Also, your party doesn't have to stick together. You can play on the same map, but go off and do your own thing. I have a buddy who can't follow instructions to save his life. He's always running around, causing chaos everywhere he goes. We're trying to stealthily infiltrate a base and he just crash-lands a helicopter into it and runs in guns blazing.

So... we let him run off and grief other bases or enemies while the rest of our party focuses on the mission. Everybody wins, and we all get to play together and have a good time.

EDIT: Same goes for Tom Clancy's The Division and The Division 2. Unlike Breakpoint, which takes place on an island nation, fighting against a wannabe dictator, The Division takes place in America after a virus plague has wiped out most of civilization, and you're playing as an elite team that's trying to restore order to the population.

I've been playing The Division with my friends for a few years now. It's a very fun game series.