I like to solo. It is addictive. But hard to get good enough to solo at a high level unless you have good partners. Not impossible mind you but at least for me just not likely to be able to get the "miles" in to be comfortable on something I find interesting. Read "challenging" into interesting if you like. But grades don't matter...what ever level you find interesting.
For me at any rate it really boils down to having a good partner or better yet, a small group of good partners!
But they are so hard to come by. Old climbing friends may not have the drive or goals you have now. Old friends may no longer climb. New climbing partners may not have a personality you can understand let alone deal with for more than a few minutes not to mention a few stressful hours ...or better yet, back to back, stressful DAYS!
Good partners are like any good relationship. Lots of give and take, communication BOTH ways and the maturity to understand the other's weaknesses and strengths. Best to leave the ego at home. Friendly competition can be great or it can be dangerous. You can use that competition spirit to your advantage but my thought now is it is better just left home.
The best partnerships make each 1/2 better than can be on their own. I'd never solo if I had partners that always helped me climb at that level!
I've climbed so many times with partners that between the two of us we were barely as good as we needed to be. Everything was a little extra effort, needlessly so. It is a rare combination that gets up climbs that neither could do alone.
If you have had that kind of partnership you'll already know it and hopefully still be able to tap into that synergy. If you have yet to experience it keep looking! The time and energy is well worth the effort!
The most important thing? You have to be willing to get out... look around and climb with new people. Have a "student's mind". Bemoaning the fact you have no one to climb with and no time to get out....and I have done a lot of both....isn't going to get you up the next hill!