Well to give another response: Part of the whole point about there being the Temple is that finding it is important. It is this one key staircase you gotta find early on (unless you got lucky with an altar vault even earlier), which means that skipping part of a level due to a tough unique early on is a bit of a risk, and it is also a big deal if some tough enemies happened to spawn near the staircase to the Temple. That can be really frustrating if you were 100% dead-set on only worshiping one particular god, but short of that, there are several different ways of handling that kind of situation, and overall I think it is good that sometimes you are pressured as a player by having to deal with that and adapting, even if it means sometimes you can't get
exactly what you wanted/expected.
Giving a second entrance to the Temple (in effect) seems to completely detract from the point of having the Temple in the first place; at that point, you might as well remove it, which isn't going to happen.
(Bit of a tangent but you might be interested in the discussion in this thread, from a while back:
https://crawl.develz.org/tavern/viewtopic.php?f=8&t=10630)
In any case, to give the advice you asked for: Yes, if you haven't found a reasonable god choice for your character, or if there are only certain gods you want to worship and haven't found their altars yet, then you should go back and fully explore areas that you skipped. Doing otherwise is very silly.
"But hey, doesn't this mean finding the Temple is a no-brainer, I thought Crawl design is all about avoiding no-brainers!" Well, that is really an abuse of the term "no-brainer."
Worshiping a god (unless you are a demigod) is a given if you are interested in winning the game; the point is that
which god you worship provides some interesting strategic decisions (at least, ideally it does). Making sure that you find the Temple is a "no-brainer" in the same way that picking up and using good items you find is a "no-brainer." You can describe just about any feature with a sufficient level of abstraction and say "doing this is a no-brainer"; it doesn't make your argument good, it just means that you are able to hang a buzzword on a bad argument.