Extinction is pretty solid, though. It's hard - PoC is probably the only map that's really worth playing as a solo player, but the other maps are still an option if you manage to become really good at the game and/or can get a decent group playing. It's different, but at least the devs actually tried something.
I think all the maps are worth playing, but you REALLY need to grind and get gud if you're gonna play solo. I had a team back in the day and we completed all the maps, it was quite the experience, not unlike doing the easter eggs in zombies with the boys. If you missed out, well, good luck.
I liked that every map has different gimmicks, again like in Zombies. Point of Contact is kind of like Kino Der Toten, in that it's free, easier than the other maps and very replayable. Perfect map if that is all you're going to play, Nightfall got spicier but the difficulty spike got higher, doable solo if you're an expert at the game. Mayday is where the game shit the bed in solo: The map itself is fine, there is a lot of setpieces that are cool, but if you fail them then you will have to do them over again and that will get really old. Crafting helps with that, you actually get an option as to what you should spend your limited resources on so there is a bit of metagaming and experimentation here(Do you want an equivalent of monkey bombs, or maybe a really powerful set of grenades? The whole map is full of choices like this). The final boss really kills it tho, it's not that bad with friends but if everyone has a different role, but in solo it is just a giant bullet sponge that will just straight up kill you if you don't have a right build in solo, fuck that. Only play that map if you can beat the other 2 maps without a sweat.
Awakening is where the game gets weird, since we're back to the slower pacing of Point of Contact but also the setpiece gimmicks from Mayday that get old. There is also no boss battles and a timed escape sequence at the end like in Point of Contact. Not sure how to feel about this one, I think the flying enemies suck and the low atmosphere makes everything weird, not like being able to floaty moon jump helps you any with how fast and agile the enemies are.
Exodus is one of the better maps, however. There is the element of surprise with the crafting like in Mayday, but the map actually gives you options where to go instead of being linear like the other ones: You have a set objective and the map asks you which zones to clear first. You need to know which gadgets or resources you will get and metagame around that, the map introduced another set of wonder weapons and grenades too to make the map easier(Nightfall onwards has X-Venom, which is kinda like the raygun of Extinction, Mayday and Awakening has different flavors if you're into that sort of thing). There is new boss type enemies that are fun to fight and the map gets progressively harder, you will have to think twice about which areas you will leave for last. The map ends with a big crescendo event like in Left 4 Dead and the mode actually has a consistent ending without a cliffhanger, great way to end the gamemode off.
So, TL;DR if you're playing solo, get good at Point of Contact and then move on to Nightfall. Leave Mayday and Awakening alone unless you're a huge nut about the mode and then play Exodus for a grand finale. You will have a fun time. The mode actually has good story and characters and it sucks to lose out on 2/5ths of it if you skip Mayday and Awakening, but the barrier to entry is just too great for single player, take it from somebody who was crazy enough to solo every map AFTER a shitload of upgrades and after completing every single map with a skilled crew.
Oh, and there is an arcade survival mode too where all you do is shoot aliens in a small room with a score multiplier and everything, it's way more fun than it has any right to be but there just aren't enough maps for it. Fun gimmick, but the main mode is where it is at.
Oh and I know the mode TECHNICALLY got another ending in IW Zombies, but it had to retcon a ton of stuff and the map is...kind of shit? Like, everyone agrees that this one map sucks, I don't see anyone defending it, and that is one map I also hate too, I will defend literally every other one. Maybe just forget that one, Exodus has a pretty good ending on it's own.
