It is one of the best nu XCOM adjacent Tactical games actually, and it plays closer from Gears of War.
The main issue is indeed the lack of variety :
You only fight against Nurgle, but there are quite a few different opponents now after 2 years of DLC and patching (between various CSM, cultist with different loadouts, a few deamon engines), but everything is a variation of green (including the scenery), and there are not that many "standard mission". The expansions and patches added quite a few, though, but you'll play "destroy the bloom spawns", and kill the "special spreader target" a lot of times.
It still is pretty solid, with a focus on lightning strikes and melee combat, which is pretty refreshing (and makes it play very differently from NuXCOM or Phoenix Point).
The Geoscape is nothing to write home about, but it serves its purpose.
You do have a small team indeed, and they feel more like glasscannons than armored powerhouses (but actually, that is not too far from the feel of the tabletop, as Space Marines do melt under fire in all editions of 40K and epic 40K).
As for older 40K games, you have OG Chaos Gate, but it doesn't have a Geoscape, and you have a limited pool of Space Marines (50 or so, but you should have enough to last through the campaign).
It also lets you field 3 squads of 5. However, it relies on preset missions, with a some uninteresting random missions in between.
It is great from a thematic point of view, but barely replayable.
OG Chaos Gate doesn't have much more variety (Khorne Berzerkers, Word Bearers, Cultists, and a few Khorne/Tzeentch minor and greater daemons).
I wholly recommend both Chaos Gates if you haven't played them.
That is true, but the tabletop also does the same. I remember wiping every single marine (except for the commander hiding in a bunker) in a game of 40K, and losing several companies of Ultramarines in a game of Epic 40k. It is even worse in Space Hulk (and Space Crusade, but I suppose this one is no more cannon).
