What will we not get without Endwalker?

[Shougun]

Island Sanctuaries
New raids and an end to the main narrative
Upgraded jobs
Ishgard housing
Etc.

I think they meant without buying the expansion, say for example Ishgard housing is probably going to be regardless of expansion status- since if a FC had ishgard housing and you didn't own the expansion would the game be like "LUL, NO FC FOR YOU".

On the question from OP I think people answered without a lot of points so I'll go generic and simple (but a bit flawed) then:

Anything post level 80. Which therefore would include the gear, quests, areas, and so on that rely on that post level 80 concept.