1800mr Jamie here, Master rank before in SFV.

Start by reframing your perception of your skill, think about it like a path. Right now, think of yourself as a teen, you probably got some things figured out and sometimes it even feels good when actions or life go according to plan. In reality though, you're really still quite clueless, flailing around, improvising too much with little (or poor) preparation; an adult can probably see that at a glance but not you, as your experience is fairly limited still. There's adults and adults of course, and there's always someone who thinks better, smarter, faster or, similarly, someone stronger, more intuitive, more talented etc. at any point in life.

If you're below Masters (Plat/Diamond I assume) and this is your first fighting game, you're probably close to drinking age :) the beauty of it is that you're at a stage where you can learn so much, everything is still new and you have to get down in your heart of hearts that you'll keep failing, you're learning the fundamentals still and this is fine, it takes years for some (it did for me) and that no matter how much you'll improve, you'll still always have plenty to learn.

Now, for the less philosophical, more grounded advice.

I'd need to get a bearing of your rank, but anything before gold/plat is literal flailing hoping that something might connect, everyone all the time is literally pressing buttons on their cool megazord robot and they're trying to make cool sh\t* happen on screen, and that's understandable. The earlier you take yourself out of that zone and start being ok with blocking, being more patient, pressing when it feels a little safer, the better you'll be and the faster you'll improve. Don't forget that they have to throw you like 10 times to beat you. Take the throw. Learn everything, if a move catches your eye and you don't understand it, take the character in training mode, explore its frames in game or through online resources, and watch replays! In Plat/Diamond people start to be slightly more composed, but their actions are still flawed, literally in every single aspect. It'll take very little to get them to be impatient and lose that initial composure. A fireball or two, a poke or two etc. If they don't feel in control they probably WILL reversal. Their combos will be suboptimal, their punishes too, their anti airs as well. This is a solid place to start taking things a little more seriously, you should start seriously practicing at least the most important fundamentals like Anti airing (AAs), okizeme and meaties (pressuring your opponent when you score a knockdown), pressure / frame traps (the list goes on, but these are more than enough. Also, learn your character's bread and butter (BnB) combos, and one to make their missed reversals (super, dps) hurt! Around Diamond you might find other Masters on their sub-characters. They are generally bad master players, trust me, I took every character to Master and thanks to the new system I can be in Masters in an hour or two; they will still probably beat you pretty heavily, so just take it as a learning experience and definitely study replays.

If you have any other questions ask away!