A lot of famous rpgs have companions, followers for the player character; aboslute solo adventures are rare. They're either part of the group, or temporary for the length of a quest.
In fact with a lot of famous rpgs, the group is often around six, and often, better for it. You can play divinity original sin with one character (so I hear,) but I wouldn't want to, personally. Baldur's Gate, Mass Effect, Knights of the Old republic, Dragon Age, etc, lots of famous companion characters. In fact for me the companion characters were the spotlight of those games.

But I think anyone who tries to make a group of six people in a Bethesda engine game (including New Vegas here), even if a _very_ talented modder were involved, would find the results... not so great. Normally I loved the big groups of bickering characters.
I've tried multiple companion mods in Fallout and Skyrim games, and they didn't cause me to enjoy the game more, to put it politely. Even the original two fallout games, more than one companion could result in all kinds of tragi-comic crossfire disasters if you let them have explosives or automatic weapons. Does that make elder scrolls and Fallout almost unique, in that regard?
Or maybe I'm way off and people loved playing Skyrim with six followers chopping their way through the dungeon?

You could point out that, perhaps, these games' characters weren't programmed to work in a group, and were designed to be a lone follower (Inigo and Vilya being an amazingly rare exception.) Lydia and some other rando are just human-shaped swords to carry my burudens, so of course a hoard of them isn't going to make the game more interesting, right? But a lot of RPGs like Icewind Dale had 6 characters, each with far less personality than Lydia.

Not sure if i understood your post - so many topics
If You like soloing try Gothic series (if you hadnt), crappy graphic and HORRIBLE controlls and mechanics but interesting plot and somehow enjoyable. Also Dark Souls are solo rpgs
For beth games i recommend Toaster mods - recruit EVERYONE, no friendly fire etc
About tragi-comic crossfire, how many times as n00b did i burn my warriors with wrong spell in Icewind Dale
Have to agree most companions are mobile backpacks, agro range are weird - some will snipe the shit out of enemies but mostly they will look at you while getting smashed by group of supermutants

Try MMO? When you want you can group with others, when not travel solo or bring 1 friend. Its funnier to have thinking companion without micromanaging

I can sum up by saying that Bethesda's engine for Elder Scrolls and Fallout (including Obsidian's New Vegas) doesn't seem to be as conducive to three+ party groups as games like Baldur's Gate, Planescape Torment, Pillars of Eternity, Knights of the Old Republic, Mass Effect etc (which I feel, each thrived on the group.)
Its' sort of a shame, I suppose.  We probably won't ever see a Fallout 5 or Elder scrolls game with a bickering, neurotic party of six adventurers.  It's be a completely chaotic mess in combat I think.

Ehh... I wouldn't really enjoy that amount of people in a party at a given time.

Especially in FNV, I've found most companions to be a liability who either kill all the enemies thus removing the balance of the fights or die immediately. It's certainly no where near a turn-based RPG nor does the engine allow you to face such hoards of enemies that having that many companions would make sense.

On the other hand if you're trying to roleplay a character who's an absolute untouchable badass, having a squad of companions rip through enemies for you can be a positive thing.

Also, it would be nice if future fallout games allowed for at least 1 or 2 more companions and added bickering.

On the other hand if you're trying to roleplay a character who's an absolute untouchable badass, having a squad of companions rip through enemies for you can be a positive thing.

Also, it would be nice if future fallout games allowed for at least 1 or 2 more companions and added bickering.

I agree more than 2 followers at a time would be chaotic, also navigating indoor spaces may be impossible the buildings just aren't made for that much traffic in Bethesda games. FNV does have Willow and Niner which are great companions with their own quests. They work well together, not quite Inigo and Vilya but close.

5 companions plus PC in Baldur's Gate, Planescape Torment, Icewind Dale, Tyranny, PoE, Pathfinder Kingmaker and etc, works because every character have a role that is needed to progress more easily, yes you can play solo builds or less companions for the challenge.

Yeah it.d be nice to see party banter in fallout someday

I guess the biggest obstacle in this is the fact that games such as Baldur's Gate, POE, etc are completely different games from the modern Fallout games and Elder Scrolls.

The modern Fallout is an FPS/adventure with RPG elements (with FNV having more RPG and FO4 having less). Elder Scrolls was a medieval life sim/ dungeon crawler then an action adventure with RPG elements. Implementing something like companion banter among 4+ characters like from BG/others would be very challenging to say the least.