I can't seem to improve my smash

Is this the "Please google me all pros explain smashing videos because I didn't improved since a match from 1.5 years ago" thread?

 

You're actually a pretty decent player.Like your footwork and you've got a good jump.
The more you want to hit big smashes, the slower they end up going, in my experience. Double this when you start overthinking it.
You've got good enough mechanics, (my footwork and stroke cycle are much worse than yours) but I can (could: injured now) hit far harder every time. Because I'm not tensing my grip. Its like Momota's video says. Just the bare minimum of finger pressure until the point of contact.
I'd actually think about your grip size maybe - if you've larger than average hands and you're playing with eg a yonex 5g grip, you'll be choked up on your swing.
What else? Backswing looks rushed. Relax. You watch Lin Dan, he seems to take ages, just stretch back like you're yawning - you're not pulling back deep enough or long enough. You've got time - loads, with the jump you're getting. Don't rush it. They are microseconds for your opponent to **** himself and if you're lucky, move before you hit.
I would play half-court for a while concentrating on it. Make your job easier and just do the walking version and standing version of your smash, rather than the jump. In fact, before that, just walk through your stroke cycle as slowly and smoothly as you can to warm up. Get into a rhythm, and don't think about speed. Speed will come.
Also work on the straight smash mostly - that's why half-court. It's the bread-and-butter shot. But honestly it's the money shot. Cross court is lower %, when you need it, you'll probably miss. I was a very mediocre singles player with only 3 good facets to my game: a really good high serve, a highly accurate deep clear - and a very hard very accurate straight smash up the line on both sides. Despite this, I've caused problems to serious players. Because I knew my strengths and weaknesses. You are trying to do too much - eg. you throw that first smash full power cross court while backing away from an aggressive clear. To your credit, it goes where you want, but dude, that's Kento Momota/ LCW territory. (And your opponent if he played a straight drive would get a winner there.) unlike gymnastics you don't get bonus points for difficulty! (why not straight punch clear? You might well get a weaker return to take your time with) Then you play an excellent net, and the second one is easier off his lift. Third one.. lol. it happens. i think the luck you used up earlier ran out.
(Modern male MS pros set a bad example for us mere mortals. Because of modern rackets & perfect technique they try to play pattern-less singles by and large, and the guy with the better technique and/or stamina tends to win. My coach was always adamant that cross-court smash in singles was lazy reductive thinking unless you're doing it for a tactical reason, its actually easier to **** someone over working them on the same side before going for the kill, if you smash xc and if he blocks it straight you're the one out of position. So it has to be a winner, and it's a low % shot as well.
i'll get off my soapbox now.)
***Another thing to think about. High-percentage smash that can change your life bro. Body smash. I had a guy in uni who could cope with the heaviest smashes i delivered down the lines. I was sick of winning the first game wasting my energy and getting tired having to keep hitting one more smash, and losing in 3. Body smash is a different facet of his defence to test. Your margin for error is huge, his return angles are easier for you to follow up on, also he has to think about grip changes both to make the shot and afterward, he can't just cruise around with a long grip all game as some singles players do. it makes him think.

 

I suggest you try experimenting outside of a game, with smashes done without a jump. and without a scissor kick.

So for example this kind of very simple thing with the feet here, on the floor, in Axelson's video "BEST TIPS TO IMPROVE YOUR SMASH! (SMASH TUTORIAL)" in the first 6 seconds. See what he does with his feet with the arm action and and turning his hips.

See if that is any more powerful than the smash you do with a scissor kick or jump smash. If so then maybe it's possible to apply that in some ways to your jump smash.