As a young player I used to think the jazzier it got, the harder it got. Quite the reverse as it turns out. Not so with 'easy' chords. You've got to plan ahead a bit more, mould your melody line to fit. Like everything else about playing an instrument, or doing anything that requires motor skills, practise is the key.
Most players practise fast.
We all want to be the fastest that ever was. But practise the slow stuff too. Put time into playing slow simple melodies. Use well known melodies if you can't yet invent them. Any melody will do.