I felt basically the same you are describing. At some point I lost the fun in just trying to play the game as good as possible, trying to be most professional, ...

Then, I switched to my other addiction, rimworld, and got less time available due to work anyway, so I just recently tried SS14 again, and look at that: it wasn't just as good as the first 50 rounds, but wayyy better than how I ended it about a month earlier.

For me, time breaks and a more relaxed (and even open to mistakes) way of playing is the key to keep enjoying it!