I was reminded of this question when farming red chests in Droughts this morning. It’s a lot less fun doing chest runs like in Wildlife Preserve (my favourite) or Frostburn Canyon, as the more open level design means that getting from place to place means a lot of retreading, or just teleporting.
I quite enjoyed going through levels to open chests in BL2 and beat the respawns, but neither of those things really work as well in BL3.
I do not think that non-linear levels hurt the game.
In my opinion level design is like flavor - some like specific, other both. While linear levels provide focused experience, NL levels are more like theme parks or/and spaces to realize specific ideas (Lectracity).
Of course NL levels are not as cost efficient, as Ls - and that is for every open world game - most people go to specific place once and then move on: consume the content.
Backtracking can be good if done correctly - it shows different panorama, secrets, approches to combat (like dust2 - site retaking from tunnels and mid/ct spawn is different experience).
But it doesn’t mean that it should be thrown away - I like side quests and activities, exploration and atmosphere. Any Borderlands wouldn’t be the same if it was corridor shooter only.
Of course, if one reduces BL experience to farming only, then anything besides 2 points connected by line is time waster.
P.S.
Also, if someone is interested, I recommend checking out graph theory and its connection to movement - it might help to describe difference between Athenas and Lectracity at the most basic level. Theory usage can be expanded to sight/shooting.
tl;dr map design is hard.
I don’t know, I enjoyed Wildlife Preserve too but in BL3 I find The Anvil or Konrad’s Hold serves a similar function 
BL3 seems to have the same open-world linear level mix-n-match of the otther BL games.
I’d like a huge a HUGE amount of non linear. Promethea and Eden 6 need more maps, they are entirely populated planets. As of current the available traversable area is linear. I feel confined and especially on Promethea.
Give me a Carnivora size city scape filled with random bounties and encounters.
I’m curious what folks mean when the say “linear” maps? Linear maps to me means something like Dragon Age or Gears of War, where your path is always fixed and you may or may not be able to back-track on it.
OP mentioned the Droughts, which is not a map I would have described as linear. Main story through that map might indeed be linear, but the map itself is thoroughly explorable with multiple driving routes through it.
Correct, Droughts is open world, non-linear.
Linear is, to oversimplify it, the opposite of open world level design. The level has a clear beginning and an end, perhaps with or without branching paths between.
In hindsight, a lot of BL3 levels work that way, so I may have been mistaken.
The one you drive through with the thingummy macguffin that Tannis needs is definitely linear. And, if you skip side quests, the main story path on Droughts is pretty linear too.