I can count on one hand the amount of times I've been ambushed in solos. If you're getting shot in the back of the head, it's a skill issue.

Literally just play like you're always being chased. When you walk into a building, sit around the corner from the door and watch to see if anybody is following. If you have to kill a drone, look around before you loot. Set up a perimeter. Walk when you first approach a poi or building. Try not to cross open areas, and if you have to, sprint the entire way and use stims to keep up the pace. Bring smokes and lure grenades for a free extract.

>>714228440
Problem with MGS3 is that it's a vibes game.
MGS2 is a mechanical game, you use the level design and the full extent of the mechanics to traverse the environment efficiently.
MGS3 is an experiential game, you're trying to get into the role of the stalker turning the jungle against the guards and the mechanics are more in service of this roleplaying experience than efficiency - this is why stuff like the menu usage doesn't really matter since it simulates the time it'd take for you in that situation to get yourself fixed up, it adds nothing to the game mechanically but it does add to the experience.
Some people will love that kind of thing but a lot of people might also prefer the MGS2 approach, so MGS3 will never really satisfy them fully.