Big story short- were Skyrim sold the best during released period? - consoles. Did consols had mods in this period? no.
Will 7D2D be on consoles too? Yes.
You really seem to forget that you yourself put so much importance on "official" DLCs/expansions or a 7D2D 2 being better that you would surely buy it from TFP. So would I because as you said a DLC or expansion or 7D2D part 2 from TFP would automatically be canon. And it will be canon for a lot of mods as well because they probably want to use features newly introduced in such a DLC.
Just as a simple example: If TFP added a few workstations, legendary weapons and 1-2 new quest types. Would anyone buy such a DLC or expansion after the supply of new alphas had dried out after release? Certainly. Would the work to do that take more than 1 or 2 typical alphas now? Surely not.
"And since one of your other complaints is about graphics and style: Are there mods that improve the visuals of Bethesda games or add stuff in the same style? Yes." Well that's true - like immersive creatures , armored skeletons. a lot of armor, npc mods etc. Did 7dtd have such mods ? no. If there will be such mods in future? probably not.
At the moment TFP has a lot of support for modders who add xml changes but nearly no support for graphics mods. This depends very much on what TFP adds there in the future. But I suspect steamworks support alone will already improve the situation as it allows easier copying of whatever mods the server has installed to clients.
"Are there mods that make 7D2D massively more difficult? Yes. " Yes. But did TFP change hardcore mechanics into casual? Yes. If this influence on playbase, types of mods, visual artstyle etc? yes.
Sure, but according to your theory you yourself wouldn't be here anymore, right? (EDIT: As I haven't played anything before A15 I can't say anything about whether earlier games were more hardcore or not, I'll just assume they were for this discussion)
And had 7D2D been "casual" all the time then no harcore players would ever have played the game and stayed with it in your theory. Now at least you can assume hardcore players exist who pine for old times.
But lets look at Bethesda again, their games were never ever hardcore. Do you really want to tell me there is no hardcore mod for Skyrim or Oblivion?
https://www.nexusmods.com/skyrimspecialedition/mods/2430
https://gamerant.com/skyrim-hardest-difficulty-mods-ranked/
Sure, anything harder than vanilla can be called hardcore even if it isn't much and in your theory we are starting at the casual bottom. I won't test them out to find out if I'm right or wrong, but lets at least agree that there will be mods for 7D2D as well that add some "hardcoreness"
EDIT: And as Kosmic Kerman reminds me we already have harcore mods for 7D2D. You might not like those mods for other aspects (like uneven style or new magic zombies) but that doesn't change the fact that hardcore mods exist, right now.
"And another point: 7D2D 2 won't need 10 years of development. They will not start from zero, they will most likely start with 7D2D and just add features they didn't have time for to include in 7D2D." Small sec... here we go Mount and blade - 2008, Warband 2010 ( warband is very expended M&B but using this same engine most this same assets etc.), Mount and blade Bannerlord - 2020 early access 2022 final version --> 10 years.
So - 7DTD is very moddable so people won't buy 7dtd 2 if there only few features will be added - it has to be higher tier of quality right? But this mean time. Now if i good remember - they are working on 2 - 3 games - we don't know anything about this game so it's hard to say how big this game will be - this can be something small like 'Wicked" or "Cult of the lamb" or big like well... 7dtd or terraria
M&B to Warband was just 2 years because they used the same engine and most assets. Voila. And did Warband sell well? While we don't know, player satisfaction with Warband seemes to be great and they released 2 DLCs for it so it can't have been a failure.
What else does your example tell us? That it can take from 2 to 10 years for another version. Sure, if TFP really thinks they need to make a new engine for 7D2D then yes, they will need a lot more than 2 years.
Higher tier of quality? Do you think that warband was made with a lower tier of quality? If not and they did warband in the same quality as Mount&Blade, why did it take them only 2 years? And why couldn't TFP do the same?
Yes, they are working on more than one game. As you probably know that is very normal to have designers switch to designing the next game while the previous game is still in production. And we know they hired new staff for some unknown game in the unreal engine, so it is not impossible but also not likely that it will influence development on 7D2D.
Whether all of this leads to less developers for 7D2D 2 we don't know, but TFP has all the cards in their hands. If they want the same team and team size on 7D2D 2, there is nothing preventing them.