Xcom 1 and Xcom 2 there are no real tricks to RNG.
that's not exactly true, the strategy with Xcom 1 at least was to try and get to the point where you had all the guaranteed hit abilities than just chain in the zone and close combat as much as possible in a single turn. The hard part of Xcom 1 is actually the early game because you are forced into RNG, but grenades are still 100% chance to hit. In fact the only part of the game that you can't avoid RNG is the airbattles which I think even in Vanilla were the hardest part about it, if you lost the air game you were pretty screwed. The mitigation is to build lots of the consumable items to make the air game easier but its not exactly an I win button in the same way In The Zone and Close Combat are. And keep in mind that the EU experience was very inferior to the EW experience. EW did a lot to try and level out the playing field a bit so it was at least challenging. Vanilla EU is a very easy game if you spec your troops right.
The holy trinity seemed to be, Scouts to run overwatch, Snipers to In the Zone and Assaults to Close Combat. A Gunner could be useful for taking out mechs and suppression but the games are pretty easy vanilla its easy enough to just go it with the 3.
Xcom 2 has similar strategies but its a bit more complex with WOTC because at least there it is entirely random as to when the chosen show up and what map they show up on but you're still going for those chained combos that guarantee hits. The vanilla Xcom 2 wasn't great and I found it too easy as well.
I think a better comparison is Long War EW vs OG UFO. They are both comparable experiences in terms of difficulty and complexity but I think UFO is still the better of the two experiences because of the base building and inventory management being much superior.