You're seriously complaining about that?
Caveat lector, I do not attend Pride. Yes, I'm a gay man in his mid 30s living in NYC in 2018 - but - I've been, many times. It's roughly the same thing every year and I hate large crowds of intoxicated people. It messes with my Zen, man.
That being said, I don't have a horse in the race when it comes to the demographics of Pride. Yes, it is an LGBT-centric event, but to see and hear about record numbers of heterosexuals attending sorta makes me feel nice and tingly. That means all those people are relatively OK with LGBT folks. Think about that for a second. Not only are they OK, they want to share space and celebrate with us. That's something you appreciate, not scorn.
Does anyone remember the 90s when "Fag!" and "that's gay!" were catchphrases? How about the 70s and 80s were getting caught and ID'd could land you in a hospital or worse... we've come a bit as a culture when straight people can come out to Pride and enjoy it.
Secondly, like who are all these queens of queerdom that can presume "that person appears heterosexual according to my superficial standards and thus does not belong here." Honey, you don't know that couple. You have no idea that he wears drag, and she's a paid Dom because they're in street clothes. Stop dictating who belongs "in the space." Didn't you just have a 37-reply thread on your wall about why we need to let the immigrants in? Don't see the contradiction there, do ye?
I'll welcome anyone into the queer subculture with open arms as long as they aren't trying to associate the culture with violent, pathological behavior. That's where we should draw the line, because it isn't about how you identify or what you appear as. It's how you behave, or more specifically how you treat yourself and your fellow man. Straight people are also necessary allies, they make queer babies. If they're already OK with homosexuality, think of the generations of gay kids that won't be stigmatized.
So please, appreciate the straights when they come out to Pride. Give them a high five. Loudly plot to kiss the handsome "straight" guy's cheek. Thank them for coming. Be comfortable knowing that all these people are comfortable with us. It's a good thing.