what is the best flashcard maker for studying?

Not a student but using flashcard apps for ongoing learning, mostly professional certifications and language retention, and the options I've tried so far all have a pretty obvious ceiling.

Currently alternating between a couple of things and nothing feels complete. The ones that are easy to make cards in don't have useful review scheduling, and the ones with good spaced repetition are a pain to actually build cards in. Seems like a gap nobody's really solved cleanly.

What are you using and does it actually hold up for self-directed learning outside of a school context? Specifically curious whether anyone's found something where the note-taking and the flashcard review aren't two separate workflows.