In the original XCOM my brother and I didn't realise you needed to collect and research everything. We thought it was like a horde-survival game, however it could infact be completed. Learning this years after starting to play was one of my best gaming experiences - I came back to my parents for the weekend just to blow my brother's mind!
I had a similar thing in Xcom 2 (the only one I've played) where I kept getting alerts that I needed more relay stations to contact the resistance, or something like that. Assuming these relays were on the ground, I kept doing missions hoping to find some. Eventually I found out I needed to clear rooms in my spaceship and build them myself. By that time I was seriously behind however.
I couldn't imagine storming the base on Mars with only the basic starter rifles in the MicroProse version. Though apart from the Hovertanks it might be actually doable.
That said I watched a friend play the fireaxis version of XCOM2 and he never put his troops into cover, just had them standing out in the open - yet somehow managed to beat the game using this "strategy". He blew through troops like tissues during flu season though.