Gaming

I played vanilla Stardew Valley once, and now I'm on my second go around, and I've installed a bunch of qol mods so that I don't have to keep checking the wiki and my collections to see if I should keep or sell this item I got because I don't know if I need it for an achievement, and now I have a notification that it's an NPC's birthday and I can just check to see if I own or am carrying an item they have. It just makes the game less stressful for a completionist like me.

Project Zomboid. Lots of mods that add new stuff (cars, weapons) and quality of life improvements like "Has Been Read".

Farming Simulator 22 and Snow Runner are both just absolutely different games when you add mods. The community is pretty active and the mod browser is built right into the menu, even on consoles. You can literally make your own game using mods. Without them, it could grow tiring after a while.

Some I've modded besides what you said (Bethesda RPGs would be like, 8 games or something for me) would be Cities Skylines, Deus Ex, Factorio, Stardew Valley, Mount & Blade, Terraria, S.T.A.L.K.E.R.: Shadow of Chernobyl, Stellaris, Oxygen Not Included, Project Zomboid, Darkest Dungeon, Kenshi, Battletech.

Assetto Corsa. Outlived it's shelf life by many years, and holds up to racing sims with much more modern engines, all thanks to the incredibly dedicated modding community.

Cataclysm: DDA comes with a shitton of mods bundled and is superfun

Skyrim VR. The game without mods is probably one of the worst VR games ever, but with mods it becomes one of the most fun VR games.

While not "saved" by modding, Kerbal space program is certainly not as interesting.

ARK: Survival Evolved. There are no corner pieces for sloped roofs without mods... I like a good sloped roof, and a building that's not just a square/a-frame.

Not seeing anyone mention Crusader Kings yet (unless I'm blind)

Gameplay isn't for everyone but full conversion mods let you experience basically any world you want

Warcraft 3 and the little thing called DotA.

There is no game getting worse with mods... Love my rimworld...

Sins of a Solar Empire: Rebellion has a lot of love and care put into mods. Being a sci-fi game, plenty of Star Trek / Star Wars / etc. conversions that do more than just reskin the models.

Well, as you mentioned, Bethesda games in general. I always mod Elder Scrolls and Fallout games to a ridiculous degree. But some more:

Star Wars: Knights of the Old Republic has a great modding scene. I personally find "Start as a Jedi" essential for replays. And most of the mods (including that one) work on the excellent Android port.

Also, I love randomizers. I do a Symphony of the Night randomizer run at least 4 or 5 times a year, the Super Metroid x Link to the Past combined randomizer is amazing, and I'm finally going to dip my toe into Dark Souls randomizer soonish.

Doom 1 and 2 would be a lot less interesting without mods, some of which change the game rather dramatically.

• Project Brutality turns it into a modern-ish shooter.
• Guncaster replaces the usual protagonist with a spell-casting, oversized-pistol-slinging dragon.
• DemonSteele replaces the protagonist with an anime character.
• My House and City of the Damned: Apocalypse turn it into a horror game.

Without mods, these games would have just been historical footnotes, not something a significant number of people still play.

7 days to die. The base game is in an...interesting state.

I love vanilla Terraria and Factorio but there are really fun mods out there that expand those games and don't let me play anything else!

Minecraft is an obvious answer of course, but there are some other really good games out there that get made much better with mods. Some of my favourite examples of this would be Star Wars Battlefront II (2017) with the cool hero mods and bot mods, and then Ghost Recon Wildlands with the amazing First-Person mod.

Binding of Isaac is very improved by mods. Also, even if it's more plugins than mods, but every MMOs have a lot of plugins to custom the interface and make it more efficient for the type of gameplay you want