Actually fruits are pretty great for us, if they aren’t highly processed.
Better to eat an apple than drink apple juice, also better to eat an apple than just about anything from the supermarket that isn’t fresh.
Of course, you still need a balanced diet, and you can’t get nearly all the necessary nutrients from just apples. Still, assuming an otherwise nutrient-complete diet, it’s a lot less healthy to eat a slice of frozen pizza than an apple or a banana. (the apple might even contain less available sugar than the pizza slice - people often overestimate how much sugar fruits really contain)
The “stuff removed” bit is more important than you seem to give it credit for. Take out all the fiber and water and sure it’s still the same sugars that are left over, but we didn’t evolve to consume large quantities of pure sugar, so it spikes our insulin and gets stored as excess fat.
Fruit juice is pretty unhealthy, because all the sugar is more available due to all the fiber being stripped out and you can consume a dozen apples’ worth in a few minutes, which you wouldn’t do with actual apples.
Sure, there’s not that much fiber left in raisins either. But in the context of musli they can be combined with whole grains and nuts, so you get enough fiber back to make the sugar less quickly digested and thus more healthy.
A third of the entire cereal mix being sugar is definitely worse than musli with raisins (which comes to about 10g of sugar per 100g), especially considering that a good portion of the rest of the mass in the case of musli is made up of fiber, proteins and healthy fats.
Adding sugar isn’t just “another big issue”, it’s the big issue. Eating fresh fruits is a non-issue, and usually so is eating dried fruits in moderation.