It is unclear what it means/how to complete map

Game tells you to "Complete 10 Tx maps".
I go to map, explore entire area, kill all rares I run into and then what?
Entire map is discovered.
Have I somehow missed boss or rare?
I don't know, 50+ monsters remaining.
I don't want to run around giant, mostly empty area to find them.

Game should tell you what is your objective:
kill all rares
kill boss
or both

Running in giant area to find that missing mob does not look like fun.
(I am aware of markers for rare enemies, they are not helping me here)

The objective is to kill all rares. If the map has a boss, it's kill both. That's all.

The tab overlay tells you if the map is complete, if you are unsure.

I agree that the maps are too big and running around hunting the last rare is not very fun.

The current mapping experience needs improvement. Yes, maps feel too big but I don't think this is something that can change, or that they want to change it. The overall slower pace, lack of easy mobility, and having to wander around to find all the rares just make it worse.

All else being equal, PoE 1 mapping allowed players to customize their mapping. There were mainly two ways to run maps, and both had a clear purpose: Either rush to the boss for quick completion, or run around killing everything (mostly rares) for the loot. Players did one or the other depending on what they wanted to accomplish with their endgame farming.

PoE 2 seems to be designed against quick map completion, but at the same time the way the atlas works demands from players to go through a lot of "filler" maps to accomplish anything. You can't just pick a map and run it, and you can't run the same map over and over. Even if you want to juice a map to fully clear it, that means having to run other maps first in order to it set up. And after you are done, you have to move to a new atlas area and do it all over again.

In a way, this resembles fragment farming from PoE 1, but without being able to farm efficiently. And of course there is actual fragment farming in PoE 2, which is only made worse by all this.

I think that if fast map completion was allowed, the current atlas would work very well. This doesn't mean allowing players to finish a map in under a minute; Just have one designated (and buffed) rare be the map boss, its location known from the start, and give map completion for killing it.

The requirement to kill all rares can stay as a special map mod, ideally linked with increased loot and harder map content. It also works well for maps that will regard fragments for other content. But it needs to be a special case, not required for every single map.

Make mapping meaningful - that should be the guideline. If I need to clear some maps I don't care about in order to reach the content that I want, allow me to clear those maps fast.