Why best items should be technically acquireable early. Why map-tiers should be a progression system

Ilvl in poe1 was the same way. Unlocking mods gradually might sound like a good idea at first, but you already have the mod-weighting doing that, resulting in a statistical version of that concept. Complete prevention seems bad because you just tell the player that the low ilvl loot is shit, even prior to identification.
This idea that you can't find the best shit till you're at the very end of the game is likely part of why everyone feels shoehorned to increase map tiers at an unhealthy rate, paired ofc with the ease of current progression.

Maps have tiers because they're meant to be a progression system. They definitely were for the longest time in poe1 - hell, the adjacent-maps-only system in poe1 was a lot of fun for someone like me until you practically deleted it.
Instead of copying that state, poe2 has copied the current poe1 state where you don't give two fucks about anything but the end (and I guess adjacency was considered a failure or just forgotten?).

Players naturally wanna increase map tiers if there's something that unlocks and it's not way too difficult relative to their build, i.e. the risk:reward isn't completely off (Affliction/Wildwood league). You don't need to also remove the majority of good loot. Hell, with maps scaling density/effectiveness, you're not only unable to find proper ilvl gear, you're also getting less. Hence, an argument can be made to remove one.

Right now, the map progression system only makes any sense in SSF, which is backwards as hell because the game is supposedly balanced around trading. If drops weren't so back-loaded, people would be more inclined to engage with a progression system. But it's like you haven't even tried this shit and just gave up immediately, just to give the perception that everything is viable. Yea sure, it just cost your progression system in the endgame. It is ofc a total coincidence that lots of your players find it boring.