As a distinctly mediocre, lazy and easily bored amateur pianist, I've found that selecting the right pieces for building up technique makes all the difference. I only play for my own enjoyment, not to perform a specific repertoire to a concert standard, so I cannot bring myself to practice scales, arpeggios, Hanon/Czerny and the rest. The best suggestion I've ever found is just playing the Chopin etudes (and the Godowsky transcriptions of them, if you can). They are just the right balance of being of immense technical value while still being musically interesting, lovely to listen to and cover almost the entire range of piano technique that exists. Furthermore, each etude is targeted at a particular aspect of technique, so it is easy to pick something that suits your particular needs. For instance, I'm learning op. 10 no. 4 right now [1] in order to strengthen my left hand and improve wrist flexibility at speed (the curse of small hands), and the improvement is palpable, even with very limited practice time.
The other thing I would say is that it really helps to have a goal to drive you. I quit playing piano for a decade and the only reason I came back to it, built up what little technique I had and persevered was because I really, really wanted to play a particular prelude by Rachmaninov, even though it was way out of my reach at the time. Finally learning it after a year or two of fairly hard work was very rewarding.
The other thing I would say is that it really helps to have a goal to drive you. I quit playing piano for a decade and the only reason I came back to it, built up what little technique I had and persevered was because I really, really wanted to play a particular prelude by Rachmaninov, even though it was way out of my reach at the time. Finally learning it after a year or two of fairly hard work was very rewarding.
[1] https://www.youtube.com/watch?v=-_eyiPKPO2U