If you don't own the land and can't demonstrate a direct, severe impact to you and yours from the actions of someone else, you shouldn't have a say.
"More traffic" is not sufficient. I can actually sort of believe shade from an apartment building could count, but the impression I get is that is rarely a good-faith argument (and in any case it should only severely affect a few people in any new development, so you could easily justify just compensating them in some way rather than outright blocking a development.
