Congrats on the positive transformation with a quality diet
Under 6 month old gliders usually grow into liking meal worms and fruits n veg. They are still young and have relatively recently been weened. New foods to them can take time, they may not seem to like fruits n veg yet either but keep giving it to them and they will grow right into them.
You can cut the mealies in half so they get a good taste of it, it's gross but sometimes that speeds it up and is the turning point
I've had some very young ones right out of pouch love them but only because they would taste their parents meal worms that were mostly eaten and dropped to get a new one.
The parents had already gotten through the shell so the babies reaped the rewards which gave them a head start on loving mealies.
Cutting a mealie up to expose the flesh is just mimicking how the babies were naturally exposed to new foods by their parents.