The point is that Level on classes/weapons/account level DOESN'T show your actual skill. Each player is an individual with different amount of skill. Some people can play for 200 hours and still be bad/average, meanwhile others are more skilled and can beat the game on Insane after just a few attempts.
Perfect example, you can look at any game with ranked game modes. Some people play a game for 5+ years and they are still low rank, while others reach the highest rank after just a few months...
Therefore, restriction like this makes no sense at all.
The game is low on content, hardening to open very hard and inane helps to players keep playing.
You don't get any extra content that way, it would just annoy players and make them leave even faster.
Lv30 to be able to play on Very Hard means that Hard difficulty would be max a new player can play. And let me tell you what, Hard difficulty is easy af, the first time I turned on the game, I played all game on Hard with Lv1 classes and weapons.
Lv30 on all classes to play Insane, means that you have to play this game for 100+ hours just to "unlock" Insane??? In future, they have even harder diffuculty planned, what requirements would you come up for that? Have all PvE and PvP classes maxed out to play it? Bullshit.
I bet you don't think that probably half of the players aren't playing this game hardcore. Many of them play it just to chill for 1-2 hrs per day(on average: some days they might play 4-5 hrs, some days they don't play at all). Adding such a restriction on difficulty would mean that they'd have to play for 1-2 months on BORING AND NON-CHALLENGING difficulty to unlock a harder difficulty. Does it still sound like a good idea to you?
Another thing, what if person doesn't like a certain class? Yet he would be FORCED to level it up just to unlock a more challenging difficulty?
1 - what do you mean? You upgrade weapons and choose perks for your class. Really simple, doesnt require explanation.
2 - ??? - there are ammo boxes that give you ammo. This is literally the most basic thing in the game.
3 - you can switch weapons anytime you want... again, I have no clue what you are talking about.
4 - Yes, there is... 2 ways to do that actually.
5 - the game literally tells you everything and shows each Objective you have to do...
6 - you can Vault over certain objects. No idea how it's possible to "get stuck" in linear game like this...
Overall, all "problems" you mentioned either makes no sense or are non-existent, which makes me think that you are just a troll trying to trash talk the game because this isn't even your first post where you make up "problems" that don't even exist.
CHARACTER'S ARE SLOW AS SHIT! - maybe they are running/sprinting while you are not OR you ran out of stamina and became slower. Also, not sure, but I think there is a class that has perk to increase movement speed (again, not sure about this one)
BAD HEALTH/HEALTH SYSTEM DESIGN - ??? - there are health kits that restore health, Medics also have Stim Guns that give you temporary HP. As for other 2 - Yes, that is true but "Is it necessary?" - No, not really.
DAMAGE SYSTEM MAKES NO SENSE - stop lying to us and yourself, that has never happened. On same difficulty damage is somewhat consistent. Maybe you played on Insane instead of Normal OR you got hit by multiple zombies at once OR maybe you got hit by friendly fire without noticing it (on higher difficulties, your teammates can hit you really hard).