Yeah, the mat list is the only useful thing from the DSS, but you can also get that from tooling around a surface in your SRV - basic experimentation. It takes a lot longer, but it is doable, and it is the only in-game benefit (aside from the aforementioned money, and engineering effects I guess) of the DSS.
The profit increase is sometimes handy, but it's far from "essential". "Serious" explorers don't have to explore for profit, and not having a DSS isn't going to turn any real exploration trip into a financial loss. Personally, I also see it optional for me because at this point in the game, money is functionally irrelevant.
Aside from that the DSS currently only gives you extra in-game trivia about a planet that doesn't affect gameplay at all. There's nothing you can "explore" or "discover" with the use of a DSS that you can't without (aside from the aforementioned non-play-effecting trivia), therefore it's not "required" for exploration.
"Required" means "you can not accomplish the task without this". You can obviously and self-evidently explore without a DSS.
All that's "required" for long-range exploration is a ship, a fuel scoop, and a basic discovery scanner. You can get to Beagle Point with that, and you can make plenty of discoveries along the way, and do a lot of exploration. Everything else beyond that just makes it varying degrees of easier, more profitable, or allows to have to be less perfect in your flying.
But yeah, this is getting off topic.
/Gonna explore in my Chieftain though
//So again, for emphasis - "Required" means "you can not accomplish the task without this". You can obviously and self-evidently explore without a DSS.