I feel like I haven't gotten any better at Python in about 2.5 years. I'm not sure if that's true or not, but it feels that way. It feels like the culture around the code has changed a bit, as least in my circles, which is primarily web development. I build and maintain rock-solid, stable software. I have all the tools I need to do so. There's nothing new or exciting for me to play with to accomplish any of these tasks anymore.
Docker is the only exception that rule that I know of. And, Kafka, if I ever get around to figuring it out :)
As to improving, I just always had a bunch of ideas, and I was always working on them. Working on one idea would teach me something, which would lead me to the next idea, etc etc.
So, build things! You'll keep getting better and better at it.
It's not an academic exercise. It's like carpentry. You get better primarily by.... doing it.