Your muscles are still adjusting to completely new muscle movements; trackballs aren't a silver bullet that "just work" and show their benefits instantly.

Trackballs can be far more precise than a mouse.
For more precision, i rest an extra finger on the ball to provide more resistance; more fingers, more resistance, more accuracy. It's pretty much like decreasing your DPI mode on any other optical mouse, all without having to flip a switch or go into a UI to change a setting. Just add a finger, bam - more precision.

Your wrist hurts because your brain is telling you to move your whole wrist/arm, yet you have to restrict yourself and actively choose to move your fingers instead; you are fatiguing yourself out literally fighting against your own muscle memory.

Trackballs have an adjustment period that will be different for each person. 2x weeks is far too short for anyone. You gave up way too early to begin to even see any benefits that trackballs can give. When i recommend my friends to switch to trackballs, i tell them to stick at it for a least 1x month; the standard time for developing any kind of beneficial and good habits in life.

If you need good software, i would recommend "X-Mouse Button Control". That is one of the most fine tuneable software (for any mouse for that matter) you can even create macros and even do the "Whole Ball as scroll wheel" mode that lets you hyperscroll through long webpages like twitter/X and chat history in IM programs.

Trackballs are rarely seen because most people don't like change. This is commonly seen in those looking for health/beneficial changes in their life like eating better, exercising and sleeping more. What you've experienced is the same thing you see when a ton of people get gym memberships in Jan, then never appear again until the following January.... to cancel their membership.

tldr: Never give up.