Why would white opening with e3 and then f4 be a bad opening?

After 1.e3 e5 2.f4 exf4 3.exf4 d5 4.d4(there is no meaning to avoid d4 , it will give your opponent even more space) you have a French exchange with an early f4. This is not considered good and I don't think that a player that starts with 1.e3 wants to play a bad French exchange but if you like it , go for it.

@Tomondo
My first criticism was that he gave these wonderful examples of games which started from the Bird's Opening. I suggest that he provide examples where white got routed to give you a fair assessment. (This is a common fallacy in all opening books.) In post #22, (I believe) that I was attacked by giving support of the move 1. e3 in post #21. (I played the Bird's almost exclusively back in the 1980s, so, although I never gave my opinion, I think it would be more relevant that a collection of good games.)

I also never suggested that the information provided wasn't useful, except for the posts which were really off topic, and instead mocked the strict interpretation provided by post #22.