I had a similar question before, and hopefully your question will be answered the same as mine. There's this chess960 discussion in r/chess What's stopping chess960 from becoming more popular? by MingusMingusMingu:
My view is that chess960 tries to solve a problem that doesn't exist and that opening theory is part of what makes chess a great game. You're welcome to disagree and prefer chess960.
However, I wonder if you think it's bad to memorise endgame theory? How to checkmate with a rook and king, what to play in certain R+p vs R endgames etc.? Nearly every chess player would improve their rating a lot more by memorising endgame theory than memorising opening theory - memorising openings has very little benefit unless you understand the resulting positions, while whether you remember your endgame theory often determines the result of the game.
Good point that Chess960 doesn't solve memorization. You should distinguish between two types of memories though - declarative and procedural.
Declarative memory is this for example: 1.e4..c5 2.Nf3. etc etc. It is basically saying "I declare that I will play e4" and "I declare that I respond with c5".
Procedural memory is this for example: "I play e4 to release my bishop", "I play c5 to claim some centre territory", "I play Nf3 to prepare castling".
Can you see the difference? Endgame memorisation is procedural too. Problem with Chess is that the opening is all declarative memory which we want to minimise because it is just empty baggage. Procedural memories tell you HOW to do something not WHAT to do. Bobby Fischer said chess was dead already 200 years ago because of the declarative memorization problem. I happen to agree with him.
Now even though we had similar questions, we might not have had the same assumption behind the question which is that both opening and endgames involve 'memory'.
But anyway the above discussion perfectly answers (at least my version of) your question:
Even though there is 'memorisation' involved in endgames, the memorisation is procedural, not declarative. Thus they'll still have to calculate. In particular, even if this pawn endgame pattern is similar to many they've seen before, they're still not exactly the same and nowhere near exactly the same. (This applies to endgames in general unless of course you get to very specific endgames like queen vs pawn on 7th rank or the square of the knight vs pawn. But even then I think those will have exceptions depending on how far away the kings are.)
So it's similar to like middlegames where they'd think 'Oh this Ruy Lopez middlegame looks a lot like this Queen's Gambit Declined middlegame' or whatever.
But it's not similar to (very early stages of) openings at all. When players have played d4, d5, c4, it's exactly the same every time. There's nothing really to calculate at their level.
The case of chess (or chess960) endgames is then the same as the case of chess960 openings: In the future chess960 might have 'openings'. But no matter how much people 'memorise', the memorisation will be procedural not declarative.
Eg in chess960 openings: Maybe people will have alarm bells when they see at the start a corner bishop diagonally opposes a corner queen like in the 2022 WFRCC Magnus vs Hikaru case but they'll still have to calculate. The most you really memorise are procedures.
Eg in chess (or chess960) endgames: Aside from those very specific cases, the most you're really armed with are procedures or principles. So you'll still have to calculate even if the positions are familiar. Actually that's all the positions are: familiar. In chess openings, I'd argue you have more than familiarity. Again, when players have played d4, d5, c4, it's exactly the same every time. It's not like csgo or basketball where when players do a certain opening strategy because the same strategy could be different depending on, resp, their economy or their height.