So, just after reading all that.
If you want compression just (pick one):
a) Use shorter length and use splitters to join.
b) Use circuit magic
c) Use mods
a) mines: Do not use a single belt running through the hole mine, but output half of it in the other direction. Join by splitter. -> compression.
a) furnaces: Do not use the default 4xIron setup, just build 8xIron, and do them shorter, splitters to join.
b) circuit magic: learn it! Time the inserters to compress the belt just right. Even with the item creep bug this is possible. (see viewtopic.php?f=7&t=54693
c) Obviously a lot want easy compression back. Go have it: https://mods.factorio.com/mods/Klonan/belt_buffer
a) is easy and vanilla
b) is magic
c) is easiest
The changes were made to improve performance. And they did, massively. Like factor 5. People seem to think the devs just have a checkbox in the dev-gui saying "inserter compression", "side loading" or "underground belt compression". Please read the FFF or at least the wiki about belt physics to get a glimpse how hard this problem really is. The devs put in a sh*tt*n of work to make factorio running as smooth as it wondrously does.