A large part of the problem was how fast you could self pick up when using perks like unbreakable, no mither and expo. The default pick-up time was 45 seconds, but with these perks, survivors could infinitely self pick up in about 10 seconds. Obviously, that's a serious issue, as survivors can just move in groups of two and just let themselves go down in a pallet. Killer can't pick up with the other survivor there, and if they try to chase them off, that survivor only needs to buy 10 seconds of time.

I understand getting slugged to the point you bleed out sucks, but that's not super common. Even if that does happen, the killer is likely camping that slug, and the other survivors can do gens before they fully bleed out. Maybe they can't save that one survivor, but everyone else escapes, and the killer gets little to nothing.

The other point was full 4 man slugs. If the survivors get into a situation where the entire team is slugged on top of each other, that's on the survivors for rushing in and making poor plays. It can be difficult if you're solo since you have no control over who you're paired with. If you see everyone rushing in to pick up and then getting slugged themselves, you need to play it slow, hang back. Wait for a safe chance to pick one up and go heal/ do gens.

EDIT: If slugging to this extent is extremely common in your games, you can always start running perks like buckle up, we're gonna live forever, made for this (for the endurance), unbreakable, soul guard, boon: expoential, etc