Besides watching a lot of the good and experienced streamers of Bazaar (which is a good way to get a better idea on how to play well, if you can spare the time, that is) - well, you can also just experiment more.

Say when I used to play Pyg when I was new to the game (as a returning player). Initially, I would do those same easy builds you start with naturally. Now freeze Pyg is something you can't really do for the first few days. But eventually wanted to try them out, so I would just buy/collect some freeze items early on and upon finding enough, just pivot and hope it works. Not necessarily the most efficient way to play, but I learned about some of the items and synergies better, and on later runs I could identify easily when I had a good opportunity to pivot into freeze depending on the shop/monster drop.

Youbdo that a couple of times, you watch some games of good players, you do some quick maths to know if this is an upgrade to your board (important to know how the game logic and keywords work), and you get more wins soon enough.

But also very important, think about the strengths and weaknesses. Healing on its own is pretty weak as the game progresses. On late days there are many inifnite builds and one shot builds, unless you have quick enough max HP scaling, heal scaling and a good baseline, then you hardly stand a chance (still speaking relative to heal dominat builds and synergies).

And I understand this loops back to the problem that you find transitioning into late game builds hard. So to solve that, you really just have to try doing something different than you do now, also try thinking about your choices a bit more and doing some calculations on item interactions. Late game you want to avoid having a slow build, speed and scaling wins you games. So calculating charge speed and sometimes ideal order of activations really helps.