I think the problem is that in current timeline of fighting games, fighting game developers barely follow the old basis where if a character is high execution, he/she should have a strong reward system for it while difficult to begin and making the move kit look impactful or drawing eyes to people (which originally was how it should be - AKA Akira from VF). DOA definitely fits the boat where you do have characters who are similar strong without any sorts of difficulty. You also have characters such as Lee Chaolan in Tekken where he's extremely high execution but for minimal rewards, which is the opposite of the original concept (looks cool and flashwork but yet the work for damage is not great so I can't blame anyone for asking what's the point which I'd feel the same way).
In my opinion, execution don't mean anything if the reward behind it means jack squat. I don't think it's a good idea to convert current characters with enhancing move difficulty when their current movekit does simple general damage, it might be better to just add/make a character to fit that forte while actually taking the original concept. The problem with Raidou is more of a universal system situation where other characters are faster than him and he does not provide strong neutral checks for him to start a proper offense, so his high execution / high reward does not initiate as one makes it out to be. His Underworld Hell drop only does a few measly points less damage than Ryu Hayabusa's Izuna Drop while Ryu Hayabusa's version on top is actually pretty damn easy due to how lenient DOA with commands, so moments like that makes you want to play Hayabusa over Raidou, Zeo was correct that I'd switch Raidou in a flash if I played against a competent speed character. Then there's also utility difficulty such as Brad Wong where it's different from execution, but rather having a huge list of a movekit and knowing when to use them. Since the movekit is so big, you are more often trying to remember the moves than actually trying to do them, so you could add that as a sort of difficulty barrier. Even glass cannon characters where they are super weak in one department but super strong in another area. Basically there are multiple types of difficulty which makes it unique somewhat, but really depends on their output and performance.
Execution these days sadly seem to be more of a dick measuring contest than having the actual meaning to why it was high execution in the first place due to how FG companies make characters now I guess so eh, can vary. On topic, I don't agree with making current characters more difficult due to how strong they are with their movekit with minimal efforts, but rather normalize the movekit comparable to other characters in terms of output (unless they took the route for high execution - high reward which should be an entirely different character rather than converting current ones).