I get very annoyed with species when they are boring. Then they go on the chopping block. Always. Otherwise I would resent the plant for offering me nothing for my work, essentialy I become a person who has no more affinity for the plant than a random person who doesnt give a damn about plants. Im not a person who categorically likes bonsai. I killed an oak prebonsai last week that I got in a package with oriental hornbeam which is what i really wanted. I gave the oak a chance, cut it to shape and gave it a couple months. There was nothing interesting about this species (probably quercus robur). No saving grace in my book.
I have a few dozen species that I in a matter of fact way believe have potential, they havent proven me wrong yet.
I believe if youre doing it right, there is a spark. Hence my signature. But none of my plants can quite provide that yet. I can barely describe it because I havent felt it much in the last 10 years. There may be separate positive feelings from things like flowers, smell etc. Or its parts of the same thing.
One of the things that hooked me at a young age was pictures of wisteria bonsai in flower.
Some recent things I liked are the flowers on my rhododendron izumi no mai, which reminds me of sugary candy (i like the asthetic, im not a glutton). Might even put a glass of color matching candy next to it some day, as decoration.
Also the new leaves on my cercidiphyllum japonicum, autumn colors of beni chidori JM and deshojo and trident. One could say I had bitter love with JM Bi-Hoo which is very beautiful but got eaten by pseudomonas and Im not willing to spray what it would need.
I should probably visit a bonsai show to better understand what i like. Probably some others should too.