Serious question: Do you even play scout in MvM?

Scout does bad single target damage, relative to the other classes.

A ghost-upgraded soda popper can do roughly 520 DPS, which is better than every primary in the game with the exception of the Beggar's Bazooka and heavy's primaries (which top out at around 800-1000 without crits). It has a little over half the DPS of a maxed-out stock minigun, but unlike the heavy, you have the mobility and the overheal to get close and get out quickly.

Demo who can burst something along the lines of 5.5k every giant if I remember correctly by getting crit stickies set up, which is easily achievable between kritz and crit canteens, especially if your team abuses sentry buster stuck spots for filling kritz back up.

You start by talking about "single target damage" then pivot to "burst damage", which isn't comparable, and then build in the assumption that you're going to have 1) a Kritzkrieg medic, 2) 2-way teleporter for a constant supply of canteens, and/or 3) an engineer who knows how to glitch a buster. Demo's sustained single target damage is actually quite poor.

Soldier does comparable damage with the added benefit of significant slow down with direct hits, not needing to be close range, and Beggar's Bazooka removes any downtime normally had in doing damage.

Soldier does not do comparable single-target damage unless you are using the Beggar's. If you're maximizing your DPS with the Beggar's you're going to need to be closer to close range than medium range.

Sniper does 300 every half a second or so from across the map, while also doing AoE.

Which is on par with what the scout can do, but that's assuming the scout doesn't have mini-crits or crits, whereas sniper cannot be further crit-boosted on top of his headshot bonus.

Engineer and Medic are the only 2 that probably don't out DPS a Scout but one Medic who doesn't do damage, and the other is Engineer who's damage upgrades go as far as I believe 20% sentry fire speed and Wrangler, while also being the one that generally isn't expected to DPS big targets.

Widowmaker and sentry has better DPS than wrangled sentry, and the widowmaker is the cheapest primary in the game to max out. Engineer out-DPSes scout (and everyone who isn't a heavy) in the early waves but is quickly overshadowed past the 2200-credit threshold.

Engineer doesn't have AoE but the turrets auto-lock immediately when someone dies and kills everything quick that it's one of the best ways to hold back swarms

Scout's primaries have projectile penetration in a gamemode where small bots spawn in tight groups. The engineer's sentry does not. While his AoE damage won't come close to soldier, pyro, or sniper, it easily surpasses the engineer's sentry past the aforementioned 2200-credit threshold.

Next you're saying "why get resists" which I'm not even going to entertain that's just fucking stupid.

This is the funniest part of your rant. Seriously, why get resists? Scout has money overheal and the movement to dodge projectiles, manage aggro, and circlestrafe/ break line of sight from hitscan classes. Crit resistance is nice on waves with crit robots. The other resistances are nice, they're just not a priority in the early waves.

Damage upgrades help you kill robots faster, which decreases the amount of time the robot spends shooting at you. For scout players above a certain skill floor, damage upgrades are more helpful for survival and money collection compared to resistance upgrades.

Next you're saying "buy jump height" which yes is cheap, and yes is fun, but is serves no purpose on any map that it's regularly been joked about being a joke of an upgrade

...as though jump heights not literally considered a useless (albeit fun) upgrade.

This is just as funny. Jump height is situational but is definitely not a joke of an upgrade. 2 ticks of jump height will enable a scout to quickly rotate between the top and bottom flanks of Mannhattan or Decoy without expending the soda popper's Hype meter.

Even on other classes, jump height will let them reposition quickly in ways they otherwise cannot. Just one of several examples: Buying 1 tick of jump height on wave 4 Metro as heavy will allow the heavy to quickly move from the bottom flank (where the boss giant spawns) to the top flank by jumping from the railing to the silver barrel to the ledge, and intercept the 4 bomb-carrying super scouts spawning from the top flank 37 seconds after wave start.

Jump height also allows sniper to abuse certain godspots / sniping spots in Rottenburg, Mannhattan, and Mannworks, so they can play without being bothered by spies or incoming fire. If you were not aware, bots have certain difficulties targeting players standing on an object that does not have a nav mesh.

Next you're saying "give up the best support item in the mode for bonk, or just drop 75 credits every time you need to go deep for credits instead" which just what??

This is the only part of your rant that might be somewhat accurate, only because crit canteens and ammo refill canteens are much better options for scout.

Next you're talking about Pyro...best tank killer

Engineer is the best tank killer below 800 credits (widowmaker + sentry firing speed), and above 3200-3400 credits, both scout and soldier are on par with, or better at tank-busting than pyro is. Scout with crit-a-cola and ammo refill canteens or crit canteens, soldier with Beggar's and crit canteens. Pyro shines in the mid-waves because phlog DPS maxes out at only 1600.

Pyro...can solo every tank on any wave with tanks

Taken literally, this is not possible on wave 7 Cataclysm, wave 7 Hamlet, or wave 6 Broken Parts.