I love Eraserhead, and yeah i agree the subtext doesn't seem to be so "sub", however in general with Lynch, i think it's a losing battle to try and eviscerate the obvious symbolism or hidden meaning of things.
He quoted the classic line "I make movies, If you want to send a message, call Western Union" more than once after all.
This is true for all art, but i believe his stuff in particular is best appreciated at a raw level, just letting the images, sounds and (what is there of a) story transport you in his dreamscape of sorts.
Trying to translate them into "oh so the flamingo is a symbol for the inevitability of death" cheapens the experience, and art in general, is bogged down by hacky symbolism like that.
There's a deeper, spiritual experience to be had with art, that's dried up and lost with that kind of analysis, imo.
Another good point of his was in relations to people asking him about the meaning of things in his movies, and he essentially went on to say that he goes to great pains to translate his inner visions and ideas to the medium of cinema, and as soon as the movie is over, people want him to translate all of that back into plain words, which is impossible and frustrating.
The movie should speak for itself, and of course if that sort of cryptic storytelling frustrates you, he isn't the director for you.
But i think, on a very basic level, this applies to all art.
