I have features I've built, and entire products for that matter, that were nothing more than a Frankenstein of things I've picked out of side projects. Sometimes I learn 2 things completely separate from each other, and then 6 months down the line have a realization that those two things would be amazing together in application.

Product focused or not, there is no reason that you should prevent yourself from learning just because it doesn't have a TLD.

Do you mean the balance of time you spend on the projects ? Or a balance of playing with new-tech versus building something useful ?

Pick what you're good at and focus on it. You can't be good at everything.