I used to post to Flickr a lot, particularly when I was participating in the "52 Week" challenge groups (4 consecutive years). I enjoyed the interaction. But the community and interaction tailed off, so by the time the annoyed the price rise for the pro account, I decided to stop paying for it. I had to cut my image collection down the keep under the 1000 limit, but I don't miss it. I did sort out my login so I can get into it, but I rarely bother and have only posted 1 image in the past 6 months just to see what happened.
It has gone downhill and even the Explore page is not as good with it pushing/prioritising images from paid pro members so you seem to often get 4 or 5 images on the page from each of the pro accounts and not so many from others.
I do use Instagram a lot now, but I have a new account which is more focused on the local area and I post images and tag them with area-specific tags. There are area-specific Instagram accounts that run local meet ups (and will re-post images if you want to allow that, which sends people your direction) and following that account and it's hashtag will allow you to connect with other local photographers/instagrammers. Doing this has been much better than my previous way of using Instagram.
It's the old adage, "you get out what you put in".
If you want to connect with others, then seek out a relevant community account, much like you would seek out a Flickr interest group.
If all you do is post an image with a few generic hashtags, then you'll not get a great deal out of it.
IG is not a photo hosting site, the images are not even brilliant resolution, but it does get your work out there and particularly if you're a working photographer, it's almost an essential these days.
Instagram can be used in different ways. There are lots of different users on it, not just other photographers and that's where it's valuable for working photographers.
Even as an amateur/hobbyist it's worth trying out, but you have to give it a little time once you're on there and find the accounts and hashtags that interest you, then you'll stop being shown stuff that doesn't interest you and your experience will improve.
As someone who shoots a fair bit of landscape stuff, I find it very good for inspiration and location ideas. But as with Flickr, the value you find in it depends a lot on what you want to get out of it.
If all you want is photo hosting then Flickr is still one of the best options. If you want community and interaction, then I'd suggest that Flickr isn't so good any more.