Are FOBs necessary to complete the game?

As I understand it, if you create a Forward Operating Base (FOB) you open yourself to being raided by other players of the game.

I do not plan on raiding other players and quiet frankly would rather just not have the hassle: I do not have much time to play games and would rather not have my hard earned soldiers and resources stolen.

Is it possible to finish all the main ops (except the FOB tutorial op 22?) without constructing a FOB?

Solution 1:

You can complete all missions without needing to touch FOBs (except for the mandatory tutorial you mentioned).

But having to go through this does open you up for invasions by other players, and unfortunately there is nothing that can be done about this as you can still be invaded whilst offline.

There is a 'cooldown' period between invasions so you won't be constantly bombarded by enemies.

I'm personally not planning on using FOBs myself in my playthrough - I've been playing since launch and have only been invaded once so far.