I don't agree at all. I understand how media can and do reinforce heteronormativity but I don't think that's the case with Friends.
Is a comedy show about 6 young friends, they have jokes about all the aspects of their life and sexuality is no different and I don't feel like they show gay people in a bad light; there were some awkward moments with Carol but it was not really because she was a lesbian, the thing is that she was Ross' wife before accepting she is a lesbian and then married a woman, that's why the whole thing was messy and gave some funny moments.
If anything I think it was kinda progressive, I know why being politically correct is important but that show is 22 years old and even though that doesn't make it better we need to understand the times and context in which the show developed, also I don't think they ever crossed a line, yeah sure, homosexuality/heterosexuality were topics they joked about but also friendship, love, sex, work, family and you could even argue religion/spirituality with Phoebe and her beliefs...
Carol and Susan got married, Chandel-Joey/Ross-Joey had some type of bromance even though they had their awkward moments, when Joey said that he had to kiss a guy Ross was like "so what? you are an actor" or when Joey and Chandler were taking care of Ross' baby and a woman thought they were gay it was funny because they were trying to flirt with her, nothing offensive about it.
I just realized I wrote such a long post

but yeah those are my thoughts, and didn't the whole main cast kissed with almost each other?

Joey kissed Chandler just because he wanted a kiss on new years, Joey kissed Ross and then said that it was one hell of a kiss, and Phoebe kissed Rachel just to see what was the big deal about it but for her it was just another kiss.