If mods are what saved Skyrim from mediocrity, they're an elegant addition to Fallout 4. While you could argue that this is a weak Fallout game (I wouldn't know; I own all of the games, but that doesn't mean I've played them), the base game is still pretty solid in terms of its gameplay and presentation. Yes, the main quest is (oh god, this will age so poorly) mid, but it's competent enough to occupy your time neatly.

I will say this; if you're going to play Fallout 4 modded, I would recommend playing on Survival with these mods:
- Gas Masks of the Wasteland,
- Agony (with the animation patch),
- Fallsouls (just make sure to configure it to your liking; I personally don't like the game not pausing, but not having the world pause when I pull up my Pip-Boy adds tension that isn't present in the base game),
- Survival Needs 76 and Hunter of the Commonwealth,
- Darker Nights and Pip-Boy Flashlight,
- Uneducated Shooter,
- Arbitration,
- Weapons of Fate,
- No Combat Boundaries,
- Realistic Ammo Magazine (not compatible with many weapon mods, but works with all base-game weapons),
- Immersive Fallout
- Enhanced Lights and FX,
- True Storms,
- WET (Water Enhancement Textures),
- True Grass,
- Badlands 2,
- Full Dialogue Interface,
- Start Me Up

And additionally:
- Pilgrim (it's not on Nexus anymore, but the mod author still has links for it up on their Discord server. Not compatible with Darker Nights, but a good substitute if you're looking for a more horror-themed atmosphere),
- Whispering Hills (I don't believe this is compatible with Pilgrim. Aside from that, it provides a very special experience that may not be to everyone's liking. I, personally, uninstalled it after a while, but if you like the idea of a Fallout and Silent Hill crossover, it's a fun time)
- Survival Options (the only reason I didn't include this is because its only function in my modlist is to include the ability to quicksave in Survival mode. You can already modify survival needs in Survival Needs 76, and Arbitration changes damage variables. But no other mod makes it so you can quicksave in Survival mode, and because I'm a cheap bastard, I like that.)
- Loot Logic and Reduction/NPC Loot Drop Rebalance (Unsure of how this works with Realistic Ammo Magazine because I haven't tried playing with both installed at once),
- Combined Arms and its expansion (Not compatible with Realistic Ammo Magazine. Combined Arms also lets you craft ammo freely, which may make any attempt at difficulty trivial. But on the flip side, these are probably some of the best weapon mods out there)
- War of the Commonwealth with the additional MCM patch (I originally had this recommended, but unconfigured, War of the Commonwealth is fucking BRUTAL. I intended to make a difficult, but fair, modlist, and having tested it myself, I can say with a certainty that I'm having a hard time recommending this one unless you have a save file that's past the starting area)

These mods will add additional layers of challenge to the game, but it should be balanced enough not to be completely unfair.