Yeah, I don't really expect anyone to change their layout so drastically. Just throwing it out there.
But as far as the problem you're having: It's not really the height that's the problem, it's the speed. Against almost the whole cast, until like 40%-60%, one full jump is enough height to catch up to your victim. But you shouldn't really be chasing after them. You should be flying up pretty much with them, maybe just a little behind as they start to gain percent. What you have to do is press jump one frame (or close to it) after the shine comes out. It should just be a tiniest little "blip" then you should be in the air getting ready to read DI.
When learning any combo, I like to ensure I conceptually understand what I'm supposed to be doing. I like to use some impractical grip where I have (for this example) my index finger on b and my middle finger on jump. This way I can press them as quickly as I want and just sort of get a feel for how fast my thumb is supposed to be moving. You will find that the distance between x to b is too great to make in the required time.
I know you don't want to hear it, but this is where I highly recommend you try to re-position your hand on the controller so your thumb rests between y, b, and a: using y to jump. I initially used x for jump too, so I understand how intuitive that feels. But there is just no way to move from x over to b as fast as you are going to need to, and it makes lasers way harder than they should be. Yeah, it's hard to learn a new button, but you'll be back to yourself in a week or two and you can begin to speed up more and learn all kinds of new tech much easier.
The other thing you may consider is using tap (the grey stick) to jump. In my experience, this leads to inconsistency as soon as you start doing faster and faster tech (especially in the heat of battle, when you are trying to move around and dodge **** too). One big problem is that it's SO easy to accidentally full hop. This can literally lose you a stock if it happens at the wrong time when you meant to short hop (and by extension, lose the game). This one is an easy habit to rid yourself of. Just go turn the option for tap jump off for a while. Again, I used to use this all the time. It's pretty easy to shine>full hop with the stick, but I though about my goals and decided it's better to just relearn now before these inputs become too entrenched to change.
Take my advice with a grain of salt. There are plenty of people who encourage you to use whatever you think feels comfortable. I think it depends on what you want out of the game.
To me, it's pretty simple. The closer the buttons are together, the faster and easier I can press them. I'll be able to play faster and longer and more consistently. Personally, that was easily worth the one or two weeks of my roommates 4 stocking me because I couldn't short hop laser properly. But now I'm the one pushing the group to improve by bringing new tech to the table, and it's no sweat.
Actually, I've gone through this transition twice. I decided to switch away from tap jump/x to y. Then, a while later, I decided to do it again with that weird layout I've been using in P:M, but I could have easily just stayed with the default melee controls. The point is, if you haven't been wavedashing for 5 or 6 years using x, then now is the time to think about how you are using your controller. If you put in work, you will see results quickly. I enjoy sitting down every day for like 10 minutes and just practicing whatever cool new thing I'm trying to use. If that means for a while I'm practicing old stuff on new buttons, big deal. It's not like I'm getting paid for every shine OOS I do or something.
(Accidental wall of text)