Awww, I'm sorry to hear that gymnastics stopped being fun for you. You're right that it's a really competition heavy sport — it's not normally something that you can just do as a fun form of movement, it's so geared towards scores and competitions. My old gym now has a lot of recreational classes for adults and children of all ages, as well as classes geared towards people who want to compete, but there was definitely nothing like that back when I was a gymnast. Luckily I was a child who was incredibly motivated by grades, scores, prizes, medals, or just the prospect of not falling off the beam in front of a whole bunch of people, so the shift towards competitive gymnastics just spurred me to work harder — but not everyone is like me!

What you're describing with your own struggles to build an exercise routine is really really hard. If the barrier is changing clothes, the only thing I can think of is making your 'day-to-day' clothes be exercises clothes (like leggings or tracksuit bottoms) on the days you want to exercise, rather than jeans. Then you don't need to change. But that may not be practical if you need to wear something more formal during the day.