Bringing up or comparing Fallout 1/2/NV to Bethesda games is irreverent here(that's a very different debate), this is in regards to Bethesda and their own games/quality.
I said limited because you're just going off critic scores alone, ignoring the other side of the equation (in hopes to back your argument or just overlooking it, I don't know). Metacritic is a fine website, but you have to look at more than just the critics. User score is more defining and where you will see the difference I'm talking about. Most couldn't care less how critics feel towards something, everyday people/fans are the ones that matter in the end, anyway. The only downfall with Metacritic and other similar websites is that anyone can write a user review and usually a lot of people just jump on the slamming or praising bandwagon so it's hard to find accurate reviews or gauge an average, but you're still able to find a general feeling over time. Steam on the other hand requires purchase before reviewing and is generally a better place to find accurate feedback. So, with that, I don't see how any of that falls flat, my original statement still holds water; F4 is among the lowest awarded and reviewed Bethesda title if you look at the whole picture.
In the end we all feel different towards everything and If you don't personally see the decline in their quality..then we'll just have to agree to disagree here and call it a day.