Hey, there’s nothing wrong with commenting on old posts. I check my reply feed daily so I’ll always see them. Personally, I find it disrespectful when people don’t reply.
It’s also not the end of the world if you don’t have great content but comment often. You’ll still benefit. And your comments come across as genuine which will mean a lot to those who read them.
Hopefully, you start to recognise which authors are likely to respond to your comments.
Keep creating content! And keep commenting too. :)
Thanks buddy!