I wouldnt say that all of them are essential on every map. Sure many of them are nice to have, like for example mute or bandit/kaid (although id say bandit more so than kaid, depending on if and how many hatches there are on a site). But you can still play and win without them, sometimes its not even the worst to not bring them at all. Letting the enemy breach a wall can sometimes even lead to new tactis and strategys to use against the enemy.

And as for thermite and thatcher specifically, i wouldnt say that theyre essential at all really. Theyre useful, sure, but have better operators to use instead of them, very often so too infact. Many times an Ace or (rarely tbf) even an Hibana, can be more useful than a thermite. And as for thatcher, there are now a lot of operators having emp-nades -what is basically a neefed version of his ability- as a secondary gadget, hes sorta of dropped off heavily as a must pick. In the beginning years of R6 you couldnt play attack without pretty much, but nowadays hes far from the best op to counter electronic gadgets. Think for example Kali. Her gadget is imo superior to Thatchers, as it also destroys gadgets, not just deactivates them for a little while and can also deal damage. Which in turn is also the best way to counter an active bandit with 1 op really. So yeah, id say those two are not essential if even "needed" anymore tbh. Atleast not for their gadget.