I find the subject of canon for Fallout very difficult after a complete different company bought up the IP, and put people on it who have never worked on the IP before, and who quite clearly have little understanding of it.
This makes a good case why IPs should not be passed on or sold to other companies as we have seen this type of situation repeatedly.
Yet we have also seen example of one creation being followed up with a sequel by someone other than the original creator(s) that works incredibly well and feels like a genuine sequel, sidequel, etc.
But it is rare.
I personally genuinely hate Bethesda's entries in the Fallout series and all the retcons but also a lot of new additions they added to the lore, such as the Enclave surviving and being more widespread, zombie Ghouls, the overuse of FEV and Super Mutants, their obsession with the Brotherhood of Steel.
They think Fallout is all about recurring elements and making these into stereotypes and adding nonsense like real aliens and supernatural elements (the ghost should not have appeared in Fallout 2).
Worse is, there is little chance that they will ever loose the IP now so that another company could possibly undo the damage that Bethesda has done to it.
Commercial wise, Fallout is beyond the point of return.
In time people will forget that there was a Fallout 1 and 2, and believe that Fallout 3 and 4 set the standard with Fallout New Vegas being this weird outlier.
Not even a spin off by Obsidian can change that any more.
In that regard it was wiser to work on a complete new IP, too bad that one fell flat.