Not OP, but in most of my PnP 5e campaigns - both official modules and homebrew - Plate Mail is usually acquirable around levels 4-6, notably earlier than level 8.
Homebrew perhaps but definitely not the official modules.
Not sure what tier system you're using but +1 light and medium armors are still tier 1 magic items. (I'm using the game's own tier definitions, T1 being level 1-4 of play).
We have early access to ring mail. I do agree we should at least have access to chain mail. By RAW fighters and life clerics should be able to have chain mail in their starting equipment. I can even agree that we should have access to split in the early stages of the game. There's zero reason we should have access to plate armor in the first 4 levels of play though.
As for "nerfing STR fighters" you're electing to ignore shields. Yes, you can go 2-handed for more damage and sacrifice AC, but your average sword and board fighter tends to have a better AC than an 18 DEX rogue in +1 studded leather. Even with what is currently in game, ring mail + shield is a 17 AC putting them on par with everyone else and still well-suited to the tank role with second wind.
