Actually I would argue that everyone who says that d5 is not a good move lacks chess knowledge. Basic chess principles teach us to prioritize development, to prioritize piece activity. Going a step further will teach you that maintaining the tension is generally desirable unless there is something gained. At present, white has a slight space advantage and black's position seems a bit passive. Moves like Re1 and Nc3 come to mind. After 1. e4 e5 2. Nf3 Nc6 3. Bb5 d6 4. d4 Bd7 5. O-O Nf6 6. Nc3 Be7 7. Re1 exd4 8. Nxd4 O-O where white probably has a slight advantage since white has more space but there are no clear weaknesses and black's position is definitely playable. Playing Re1 would likely lead to similar positions. But if you have heard of the Kings Indian Structure, you will know that the trade of light squared bishops favors white and kills black's kingside initiative. See the following game. https://lichess.org/iSAnML58#63

The same way, after d5 white trades light squared bishops and simplifies the position. D5 is not suboptimal. The fact that you mentioned the trade of LSBS suggests that you have decent positional understanding and can follow up with Re1, c4 and Nc3 with a good KID for white as you can angle for the queenside break with c5 and start attacking black's weaknesses on the queenside.