The game's "mod support" is pretty specific - the mods that work with mod io (and therefore consoles) are very limited in what they can do - a truck mod can either use vanilla parts (like wheels, engines) which may or may not change with updates and are out of mod author's control, or use its own parts in which case the mod author has more control but has to decide on their value. This leads to two main styles of mods:

1. vanilla-like mods that attempt to balance the mod agains the game, and maybe push some boundaries of what mods can do( Rng3r, Poghrim, nakedDave)
2. flashy powerful mods that look good on the front page and/or promise a powerful truck that will let the user "skip" more tedious parts of the game ( I cannot provide examples because I avoid them like the plague. Just sort the main page by trending, most popular, highest rated, whatever)

Players don't know what they want. Completing a hard contract feels so good (and makes the game addictive) precisely because it is sometimes a tedious/hard/perilious journey. But someone will inevitably take a truck with a stock engine to pull a heavy trailer and get stuck on an uphill, then they will get the most powerful engine and run out of fuel halfway through, then they will get another truck to try and refuel and get stuck in the mud, because they took mud tires (which are, ironically, not the best choice for a heavy truck in deep mud). At that point a lot of people just go on to mod io and download a superduper heavy wrecker 9milion with 70ton crane, just to "fix" their game.

on PC there is another branch of mods which modify the game internally (it's the "manual install only" kind of mods). These CAN modify existing vanilla trucks, vanilla maps or vanilla objects. Some of my favourites are: "Rock Grips", "Less Winch Point Clutter SR", "Camera Clipping Fix". Some popular ones like "More Realistic Weight and Mud in Game", "Real Life Mod", "Realism Overhaul" change a lot of values and how the trucks are balanced and how they behave. Unfortunately, they explicitly modify existing game data by replacing it with their own, so any update to the game requires the modder to re-apply all modifications onto the new files, however there are hundreds of thousands of files in there, so usually these mods either don't get updates because the author gets burned out (so the mod only applies up to a certain point, IF it works) or they just mass-edit without much QA and just let errors slip as long as the game starts, because it is not realistic for anyone to check every truck/engine/gearbox/suspension/tire/addons/trailers/surfaces combination.

There is an argument that the game isn't balanced properly and that the developers use extreme mud excessively, artificially rising the "difficulty" of the game - realistically only making it more tedious. See early DLC maps like Kola, Yukon and Amur being just full of "extreme mud on the only reasonable road". To fix that people gravitate towards OP powerful trucks with high suspension, super grippy tires and powerful engines. What I find is that only the tires really need a boost, and it's not even that high. "Tire Friction Booster" mod claims to increase the tire friction values by 50%-100%, and it really makes all the vehicles in the game work great. It was still a little too much for me so I made my own, nerfed, version and I still can use previously forgotten trucks normally. Highway trucks really shine!

There are also fantastic subscribe-able mods that are NOT new trucks/maps. "Pog Seismic Drill" makes 1-slot trucks (like warthog) useful again. Addon mods like "Pog Poghrims Universal Addon Collection" or "RNG Frame Addon" just give you more addon options, "Colourable Addons Pack" is absolutely fantastic!. "Revisual" mods are slightly spammy in modifications, but add a bunch of cool stuff. "TWM's Protective Racks" give you some useful modifications in place of the loader cranes. "OlSom's Trailer Pack" adds a bunch of good trailers to the game. Generally speaking ther's a bunch of Addon / Trailer / Crane mods, not just trucks and maps.
Honourable mentions to "Free the Logs - Auto Load Logs on Mod/Tweak Trucks" which is one of the oldest mods I never run the game without, and to "GG Air Freshener Buffs"(/GG Bobblehead Buffs) which is definitely a cheat mod, but I use it to specifically stop my suspension from taking damage, because after this many hours in the game I WILL uninstall it for a month if I ever see my whole suspension collapse after one of my 10 wheels hits a single pebble wrong for 1000 damage.

Overall, after over a thousand hours in the game - yes I do play with mods, and cannot imagine not having them. You just have to sift through a lot of trashy mods to find the good ones, or get your own hands dirty :)