You know … it actually is good game design that if you want to farm just to get recruits and 1* ascension mats to run your training camps, 1:5-8, 1:6-8, 1:7-7, and 1:8-7 cover almost as good as it gets*. There are lots of other good, valid reasons why you need or want to farm past that stage, mostly in S2. That players who have unlocked S2 and can farm there don’t grow their rosters twice as fast because they farm there makes for much more balanced gameplay.
*Farming backpacks in 2:1-7/8 Hard does considerably beat 1:5-8, but that alone isn’t game changing.