It's old, but it's an unsung hero of RTS. It won game of the year and RTS of the year but STILL people didn't seem to play it. It's too hard for most people to play, not in terms of micro but in terms of strategy. It requires more thinking as there are more options you can take than in Starcraft and you have more limited resources so you can never really choose to do all of them.
It has the most complicated mechanics of any RTS and it takes a good deal of devotion to really take the time to dig in and look up the numbers, which can't be seen directly in-game, you have to go to a website which has everything listed. There is randomness to things which some people don't like. When a unit shoots it isn't guaranteed to hit, but it's probability so you consider the average. For some units this randomness isn't felt, like from a machine gun, because there are so many bullets you don't really care if you miss a few, but if you have a tank or sniper that only shoots once every 5 seconds, when something misses you sometimes feel cheated and that you were unlucky.
There's still a community who plays it on gamereplays.org and there's another site... something like companyofheroes.something which is even more dedicated to it. They still have tournaments pretty often. The only people left playing it now are probably those who are really good at the game I imagine so it might be hard to get into it. A lot of people also don't like the slower pace of the game or the small scale (fewer units, bigger map).
The three resource system is amazing and really makes me wish games would move past just using two. "Manpower" is like minerals, but vespene gas is broken into two separate resources, "fuel" and "ammunition." Fuel is to buy higher tier units and upgrades that effect all your units where ammunition is to upgrade specific units (like to buy a bazooka for a specific squad) and to use support powers like artillery strikes. You can't guarantee you have all resources at once since you get them through map control rather than by harvesting them in your base, but it makes for interesting gameplay. Most of the time you will want fuel, but if you don't have a lot you can use ammunition to buy bazookas and kill the tanks that they buy with their fuel.
Almost every unit and weapons has it's own armor and damage type, and weapons do different damage and have different accuracy based on how close you are (SMGs do poor damage at long range but do a lot of damage at short range) so you have a lot of interesting positioning going on. If your opponent has riflemen and you have SMGs you want to get close, but how dangerous is it to move closer to enemy lines?
Then there's cover, which is directional and there is light cover, negative cover and heavy cover. Vehicles move faster on roads but people like to put landmines on roads. There's just so much in the game it's truly fantastic and every game could learn from it. Not to mention there's like 30000 voice responses for units and only like 50 units in the game, so they have something ridiculous like 600 lines each where they actually shout out about the EXACT unit that is shooting at them, where they are shooting from and what they themselves are doing. Things like:
"Lets use that wall for cover."
"Enemy riflemen/pioneers/sniper shooting at us from the right!"
"****! ****! Where did that tank come from!!?!?"
