Before I get started, I'd just like to say:

Protip: Tremulous has been in development for going on seven years now. There have been players and members of the community that have been around nearly that long. You, like a large majority of the current community (myself included) have been around for less than a year, and only joined up when Tremulous went to standalone. You haven't been playing Tremulous "for a long time". Now that we have that established, let's look at your other points:
1.) Tremulous has no storyline.
2.) Tremulous only has two opposing sides.
3.) Tremulous doesn't have enough weapons/isn't varied enough.
Tremulous has as much storyline as a
solely online multiplayer game comprised mostly of custom made maps that were
not created by the developers of the game. Humans go too far into space, run into aliens, aliens start infesting, mercenaries are brought in to fight against them. Really, you can't ask for much more than that in a freeware multiplayer FPS. Also, what's wrong with only having two sides? It seems to work well for a few other games in recent history that you might have heard of: Counter Strike, Enemy Territory, Gears of War, Battlefield series? I mean, I could go on, if you wanted me to. As far as variation goes, how much more could you possibly want? You've got two mostly balanced,
completely different teams -- both of which have multiple choices as far as what to use against the enemy (though admittedly less for the alien team). Honestly, you expect Tremulous to play like every single FPS out there? I mean, people have been playing Counter Strike, Quake 3, Enemy Territory, and other FPS games for years when there has been
little-to-no significant changes to those games within that time. I'm sorry Tremulous doesn't play exactly like FEAR, Warrock, Halo, Counter Strike, Enemy Territory, or any other standard, run and gun, make things go boom FPS.
Actually, wait. No, I most certainly am not. I like my Tremulous the way it is: a nice mixture of shooting, tactics, and base management. I like, and appreciate, the subtle differences between alien classes and human weapons. I like that the community -- that is, the actual members of the community and not the people that play Tremulous like idiots and only chime in with ideas like "OMG ROCKET LAUNCHER FLYING ALIEN HUMANS NEED MORE POWER" -- has a decent amount of input on the game. I even like the way I can play on tjw's server to see the changes that
will be made to Trem, and appreciate that these changes have been well thought out and tested, and that they
work.
The only thing I
am sorry about is that you happen to have such a short attention span that you lose interest in
what could very well be the greatest freeware shooter in existence, which has
endless replayability and new maps made constantly, in under a year.
tl;dr:Sorry you have ADHD. Gtfo.