In a few interviews:
Hiroyuki Yamaga: May 1998 issue of "Evangelion":
On the reasons for use of Judeo-Christian symbology in Eva
YAMAGA: I don’t know exactly why. I suspect that Mr. Anno may have read some book on it, and there was some thoughts he wanted to express on it. I personally am glad that, rather than Christianity, he didn’t express some obscure Buddhist theme, because then it would have been linked more with Aum Shinri Kyo. [LAUGHS]
Kazuya Tsurumaki: Q&A from "Amusing Himself to Death":
Can you explain the symbolism of the cross in Evangelion?
Kazuya Tsurumaki: There are a lot of giant robot shows in Japan, and we did want our story to have a religious theme to help distinguish us. Because Christianity is an uncommon religion in Japan we thought it would be mysterious. None of the staff who worked on Eva are Christians. There is no actual Christian meaning to the show, we just thought the visual symbols of Christianity look cool. If we had known the show would get distributed in the US and Europe we might have rethought that choice.
and from an NHK special "Extra Curricular Lesson with Hideaki Anno", a student asks:
"Why is that robot-looking thing called an Evangelion"?
Anno: "It is a Christian word meaning Fukuin or Gospel and it's supposed to bring blessings. Actually, it's a Greek word. I used it because it sounds complicated"
So it seems the creators didn't mean for there to be any deeper religious meaning from all the religious symbolism. That doesn't mean that there isn't in-universe meaning to the show. For example, the name of the Angels correspond to their features (e.g. "Gaghiel" = "Fish", "Israfel" = "Music", "Sahaquiel" = "Sky", etc), and the symbols themselves aren't haphazardly placed. There could very well be an in-universe explanation for why the symbolism is there at all, possibly inherited from the Angels themselves or created by Seele.
Additionally, there could be meaning derived from the symbolism beyond what the creators originally intended.