The biggest competitor to Star Citizen right now is Elite: Dangerous. I've played it a lot and it's pretty good. You can play solo or online, too. It can feel a bit slow and it doesn't hold your hand when it comes to learning how to play. There's combat, trading, and exploration. Also pretty active communities online.
If you want to go back in time a bit, there's also the X series from Egosoft that's spanned back many years. There are a few installments and more is being developed. These games are definitely more colorful in several ways than Elite: Dangerous. More of a focus on the Rule of Cool than trying to be real sims.
Haven't played Star Wars: Squadrons, so I don't know the state of the multiplayer side of things. It does offer a solo story mode, apparently. May be worth looking into.
Every now and again I'll think about games like Freelancer, Freelancer 2, X-Wing, and the Wing Commander franchise for straight sit-in-cockpit combat action. Those are very old- early Mid 1990's to early 2000's. If you feel like something retro and can run them, those are options. I wish we had more games styled after those early space sims.