I remain generally happy with the service provided, however I have to say this is annoying.
I've long resisted clicking the "Like' button, except in certain excitable or otherwise interesting cases, because I found the "Liked" playlist to be irritating. It made it seem like it was just creating a playlist that I did not find at all useful.
Then I noticed that my choices did affect my Daily Mixes and other recommendations, so I decided to start using the likes to affect my recommendation, and, upon doing so with some success, began enthusiastically going through and liking important songs throughout my favorites. I must say, it was having a fantastic affect on my playlists, and I was more happy with my service than ever and enthusiastically dreaming of my long future listening to these wonderful playlists and recommendations.
Then I came to a limit. A limit that only obsessives like me will come to, but a frustrating one nonetheless.
I suspect it's a limit because Spotify still considers my Likes to be a Playlist rather than, say, like on Netflix, where it's primarily to gauge my tastes. This is frustrating to me, as I never considered that playlist valuable. Indeed I find it quite a nuisance. But the "Like" button I found to be a delight and caused me to spend a lot of extra time exploring and enjoying my service.
I'm sure this is just too specific a concern for any interest, but I felt the need to express it somewhere.
So it's seems like you're right, you're likes technically fall into a playlist and therefore have a limit. It does seem odd. Would be a great thing to submit under the "idea" section here in the community!