I have absolutely no idea why anyone is calling it awful. It's far from awful. It's not TF2, CSGO, Quake or whatever the fuck FPS game people want it to be, sure whatever, but it's far from actually being "awful". TF is honestly pretty fun, albeit lacking in long term replay value, which is its biggest problem.
I haven't played the game in awhile, so I'm really just going off of my experience with it pre-DLCs. There aren't a lot of weapons in the game, and not many different game modes either. Considering how the game plays, however, the lack of variety in the game modes doesn't really matter. All of the vanilla maps are awesome, on the exception of Lagoon, which is apparently terribly optimized for some people (or at least was). The weapons are your standard modern-day FPS weapons with a bit of a fictional or post-modern twist to them, mostly in design. When I last played, the shotgun was terribly overpowered if you weren't complete shit and knew what you were doing. The Smart Pistol was kind of a joke in various ways, though it still kept up on being fair. Aside from those two, everything was otherwise perfectly fine.
Like I said, it was the lack of variety that lowered its replay value, at least for me. If none of this is really a problem for you, then you should be set to play awhile. As far as playing with friends goes, you're 100% better off playing with friends. No real explanation needed here. It's just one of those games that you will get bored playing too much of at once when you're playing solo.
I'd say get it, but if you're still unsure, then pick it up whenever it goes on sale, if it's not completely dead by then.
It's kind of upsetting that it's somewhat dead though. It's really fun and isn't flooding the players with a load of bullshit like most modern AAA FPS games do. Simplicity works with this game, but people have such ridiculous standards now. Oh well, I guess.