The thing is that even Fallout 4 has good foundations, if of different character than 3/NV or the TES titles. For quite a lot of things, it's a better foundation because the settlement and weapon crafting systems can be readily reused to do a lot with relative ease compared to the shenanigans it takes to get that fluidity into prior Bethesda titles. Pretty much all the foundation issues are technical debt from building on the Gamebryo engine for 20 years.
The structure built on that foundation, however, manages to be eye-searing without paint, and the garage ("main" story) is condemned for water damage.
The foundation, the most important parts of the game which you build off of, are totally rotten.
No more skill points, SPECIAL has been gutted, perks are level-gated even harder than any other fallout game, armor mechanics use the weirdo-skyrim system instead of DR/DT, and generally it's just another FPS with RPG-lite mechanics, instead of being an RPG with FPS mechanics.
I mean for fuck sake even the dialogue system is completely assblasted, nobody can tell what the heck your character is about to say, skill checks are almost all gone (entirely replaced with Charisma checks), and the story is crap.
How can a game have good foundations when it's limited by
1: A shite game engine that barely works at the best of times
2: Terrible combat mechanics
3: Terrible story
4: Terrible RPG mechanics
In which way could the game be argued to be good, objectively? It didn't even have good graphics for the time, and ESPECIALLY now it looks dated.
Settlements and crafting is neato, until you realize settlements are more of a chore than an engaging mechanic (ahh yes my 100 defence base with 4 deathclaw pets and a bunch of turrets was damaged by raiders, SUREEEEEEEEEE).
And Crafting is just a cheeky way of level-gating damage boosts, and you ALWAYS will use the best weapon you can, so it's just weapon skills with extra steps and more hassle.
It's also immersion breaking as hell. Want to know how much damage skills added in FO1-2? ZERO PERCENT. It made you more accurate. New Vegas is guilty of this as well, to a lesser extent though.
So we're expected to believe that some ex-frozen chucklefuck can somehow make a gun propel a bullet twice as fast using little more than a typewriter, a soda can, and some cornstarch.
Edit: God I neglected to mention that getting the 'complete package', with all the creation club nonsense is going to cost a fortune as well, because while you can buy a FO4 key for chump change, creation club is all first party gated...