It's a mixed blessing. There is a reason that a tourist industry grew up in those places - there are things worth seeing. Against that, there is quite a packaged tourist product there.
Sligo is wonderful - an interesting town, surrounded by great beaches, historic sights, lakes and mountains. It's also largely off the tourist trail (except for domestic tourists). However, it's a good way away from your rough route.
Personally, I think you shouldn't miss the Dingle Peninsular or the Burren from your list. Even as tourist destinations, they are special places that should be seen.
Killarney? The real glory is in what's around it rather than the town. I'd happily opt to stay in Kenmare instead, which is almost as good a base for the area.
Kinsale? It is pretty and has some very good restaurants, but there are other very rewarding towns on the Cork coast - Schull, Baltimore, possibly Clonakilty.
I think you probably would enjoy Beara. It's the most unspoiled of the South-West's peninsulars (except for the tiny Sheep's Head) and probably gives the best real Ireland experience of them.