Three observations.
1) A couple of years ago I would have classed myself as an "intermediate level" player.
2) I'm better technically (and know more tunes) than I did two years ago.
3) I hear a *lot* more things that need to improve in my playing than I did two years back.
These days, I'd rank myself as "advanced beginning level" at best. I'm actually fairly decent - not great, but decent - at technical proficiency and knowledge of tunes. But that "knowledge of how the music *should* sound" thing is still kicking my tail.
I listen to recordings (my MP3 player is full of traditional music - big help). When work allows (or when on my computer at home) I can listen to the best. But I'm at the point when I can (usually) *hear* the correct swing and lift, but I can't always *play* with decent swing and lift.
I can even hear it (or not) in my own playing, but getting my fingers and breath to coordinate with what I *want* to hear is an ongoing process. I can play a piece through one time, and it *sounds* like a jig, or a slip jig, or a reel - then I play it again and it sounds like it was played by a robot, or I get the rhythm right but I loose track of my fingers and crash halfway through.
So it's an ongoing process. These days, I play mostly flute - whistle is reserved for times/places when I don't have the flute along (sitting at a red light in traffic, etc) or when my embouchure gives out. And I've found that having to concentrate on the basics of embouchure and breathing again has really helped my playing - once you've got the basics of whistle down it's easy to concentrate on speed and more speed to the exclusion of all else. But I'm not at the stage where I *can* play the flute that fast - so I can pay more attention to what I'm hearing (or not) in my playing.
I'd guess that most players from Ireland *are* better than I am. That's likely true for experienced players anywhere else, too. But as long as I *don't* think I'm perfect, and listen, and work on improving I can hope to get better. Who knows - someday I may be throughly mediocre by Irish standards.