No it's completely right, it's called "outsider perspective". It's hard for OP to realize they are not making an accurate observation. If you want to really work out if things are in decline, instead of finding some vague feeling of what it used to be like vs now, actually measure something?

Loud motorbikes weren't invented last year, and crime isn't higher today than it was 20 years ago.

I think it's harder for other people to accept that certain things can and will decline, or that history has ebbs and flows for any dimension you care to measure, and is not just linearly getting better.

"You're just imagining it bro" is a rationalisation that lets people cling on to the Eternal Progress narrative.

What in their comment was manipulation?

They responded to "Here's some things I've noticed" with "You're old and you're imagining it".

That's not manipulation and they didn't say either of those things. It does not appear that you are responding in good faith.