In the end, I didn't get a chance to play against a fellow human. The realities of my schedule precluded it. It's probably for the best. Even if I did find someone willing to play an RTS at two in the morning, it's likely that we would have been interrupted at least once.
Which just left me with a hard-mode galactic war to get through. It wasn't actually that hard. I probably screwed things up by rushing a boss fight first thing, and subsequently getting a lot of technology for free, but perhaps it should not have been so easy for me to rush a boss fight. After that first, somewhat tricky battle, everything else was pretty much autopilot. I've been dragging out winning the war just so I can see if there's a maximum tech level. I didn't quite make it to then end, there. I still have about 10 battles I need to go through, provided I don't want to simply dispatch the final boss.
Maybe, someday, I'll finish it out of curiosity, but seeing as I am still concurrently playing Fallout 4 (80 hours and counting), I don't really have enough time to waste on idle whimsy.
The tricky thing about Planetary Annihilation is that I'm not sure whether I wanted it to be harder. I suppose, if I wanted to look cool, I'd yawn derisively and say, "it was scarcely a challenge for one of my tactical abilities." But I don't think that would fool anyone, not unless the "my" was really sarcastic.
Like, I never even used base defenses. They were simply not necessary at "normal" and "hard" difficulty. My stockpiled troops were always sufficient to repel any of the AI's halfhearted attacks, with an attrition rate so low that the only time I really had to worry about building a second wave was when I got impatient and prematurely attacked with my first. Towards then end, I'd reduced the number of units I was building from 500+ to around 200.
I have to admit, I liked winning, but I can't help but wish that I'd been forced to win in a more epic way. More massive superweapons and planet-covering legions, and less sending out a half-dozen advanced bombers to snipe at the enemy base from beyond the range of its turrets (though, parking a couple of orbital lasers above the enemy commander and taking them out with a precision strike was always oddly satisfying).
I wonder, though, whether I would have been able to cope with an RTS of greater complexity and more demanding difficulty. Probably not. The parts of the game I enjoyed most - seeing the various units and watching my base grow - are not exactly conducive to victory, and really, the only reason I want more complexity is because then I'd have more units to look at and more base improvements to build. So, really, did I want more challenge from the game, or did I just want a different game?
Still, in the final analysis, I had fun, and that's what's important. Planetary Annihilation may not be at the top of my list for classic games, but I was pleasantly surprised to find an RTS that didn't make me want to tear my hair out in frustration. Plus, I liked the cartoony look and over-the-top scale (even if I didn't get to operate on that scale as much as I wanted to).
Planetary Annihilation therefore gets a qualified recommendation from me. It's worth playing, but if you enjoy a strategic challenge, you're almost certainly going to want to play against another human.