@ComeTalkToMe in my experience it definitely becomes less exciting but you do have to also condition it to be. So you either make yourself more exciting, or you give polite signs that you don't want them playing with dogs they don't know – or both.
I recall pupsy away from any dogs we don't already know and only let her approach dog friends if it's clear it's OK to, ie they're not actively doing training. Now she ignores most dogs and doesn't approach unless approved. We got to that point via a combination of offlead heel work and reinforcing that being near me was good, just general recall work, having her off the lead most of the time so she understood that being offlead didn't mean running away, and also being a bit standoffish to other unknown dogs and never encouraging them. Maybe the last bit is my imagination but when she was harassed while in heat I got quite tiger mum-ish about things and one day physically removed someone else's dog from our vicinity, telling it 'no, go away' and I guess giving pupsy a clear signal that I didn't want that other dog there.
All of that said, a lot of it also comes down to age and maturity. When she was B's age she was much keener on other dogs than she is now but she's two next month and it's made a whole world of difference. She is far more interested in her environment, much to most dogs' surprise.
Just keep at it, encouraging her to want to be with you and it will come. I did use my longline but in truth more often than not she learned by doing, ie being offlead and listening to my corrections if she got it wrong. I'm of the view that they can't learn to do something until they get a chance to try but I know that isn't everyone's philosophy.