My experiences with past games in the RPG genre (not necessarily made by Bethesda.) don't necessarily deliver that message.
Well yes that's certainly true (and often a matter of opinion as well.) But it's not generally for lack of trying, either. Especially in RPGs. Even in Two Worlds (which has some of the worst dialogue in an RPG I've come across in recent memory - and even pretty awful compared to other genres as well,) what's really sad is that they actually were trying to write good dialogue and implement a well-crafted storyline.
It's not like the dialogue in Two Worlds was awful because the graphics were somewhat decent, or it had a novel crafting system either. I doubt there's been many instances in the game design industry of someone saying "gee, I wish we had better writing - maybe we should have had our writers spending more time on dialogue and less time working on destructible environments," for example.
As far as Fallout 4 is concerned, it's likely safe to assume that it's going to have the same lead writers as Fallout 3, or at least a team of writers that a similiar percentage of the budget as in Fallout 3. As far as dialogue and such is concerned, what we have to hope for is that these guys improve over what they've previously done - throwing money or resources at the problem isn't likely to make that huge of an impact at this point.
So realistically, I'm not sure that the effect of adding in new gameplay elements is really going to have much of an effect on the quality of the story and writing regardless.
If adding in new stuff meant that the current mechanics and writing would somehow suffer, or affect the degree to which they're improved, then I'd say it's more important to work on those things, obviously. But otherwise, sure - I'd like to see some destructable environments. Might not make much of a difference destroying a bunch of stuff that is essentially rubble to begin with - but it would make the firefights more interesting as well. We wouldn't even necessarily need things like destroying buildings on a Mercenaries 2-type level - I'm thinking more along the lines of what the Force Unleashed was trying to do.