The game that i've sunk the most hours into is PlanetSide 2.
It's a f2p MMO/FPS which works surprisingly well at combining the MMO side with the FPS side. Of course, lots of people accuse it of being pay to win, however it's not. Unless you already have knowledge of how to use different guns in different scenarios, you won't benefit from buying in game items. And if you do, you're most likely skilled enough to use the starter items to their full potential and get just as many kills as anyone else.
Infantry play is rather technical. There's 6 main classes of infantry, however you can build a loadout to perform a specific role. The "infiltrator" for example, can be kitted out as a sniper, or as a close range assassin. The controls for infantry (and vehicles too) are very smooth and the default keybindings place everything within easy reach.
Each "map" is literally a map. They're massive, with between 30 and 80 regions to walk, drive, and fly around. The gun play is what you'd expect from an FPS, and well balanced. interaction between infantry, vehicles, and air is great, with plenty of anti-vehicle and anti-air possibilities for infantry. Dogfights require skill, not money, to win.
There are massive benefits to playing with friends (or strangers) in squads and platoons, however it's perfectly fine to play the game solo, like I usually do. There are loads of options for coordinating your squads using waypoints, vehicles, and voice chat.
The only drawbacks I can think of are that it takes a while simply to learn what everything does in the game, and that it's performance isn't the best. The game has always been on that thin line of optimisation. The majority of people play on mid or high graphics, with only those with proper gaming rigs playing on ultra. Large fights tend to drop your fps significantly due to the sheer number of meshes and particles from the hundreds of players, vehicles, and projectiles.
It will take hours to get used to the maps. There's a newbie continent called Koltyr for new players, where anyone above a certain rank can't join. It has one of each type of major base to get you used to their layouts as well as some minor bases dotted around. There are four main continents, and each one has 3 of each major base. These will always have the same layout, and have things like shield generators, spawn control units, and other obscure features. Every other base is considered a minor base, and no two minor bases are the same. This means that to know your way around, you need to pay close attention to your map until you start to learn certain bases.
Luckily, the map designers were somewhat lazy and used prefabs to make each base. This means that each base will be a different combination of the same buildings and rooms, so you will often recognise parts of bases from other bases. This helps a little.
After over 270 hours, I now know the layout of 90% of the bases, and know which bases are north, south, east, and west of them and the best way to get there by land. I like this game.
Here's some of my own gameplay:
https://plays.tv/video/586a7fc488572a5ed...?from=user
EDIT: "No two minor bases are the same" well, technically there's thing like Construction site Alpha, Construction site Beta, etc etc which are the same, however these were intended to be placeholders until different bases could be added. They still haven't added those bases.