What it sounds like is going on here is you have entered an isolated experience with your play, where you aren't able to continuously improve and learn from other people.
Find the best players of the character you're most interested in. Watch their sets. Observe what moves they choose to use, when, and why. Observe what they do in certain situations that give you trouble. What do they do out of shield? How do they edge guard? How do they follow up after certain attacks? What do they punish with, when, and why? Try to learn from the best players that play a character you want to get better with.
Join the Discord for your character and read the relevant channels that discuss frame data, theorycrafting, combos, or general play with the character. You can learn a lot of tips and tricks and techniques just by watching these channels. I can pretty much guarantee the Pichu Discord is active, given how highly-represented that character is in the meta.
Watch YouTube guides for your character. You will learn things you don't know. I just learned yesterday, for example, I can save 7 frames off my sh neutral air follow-ups just by delaying my fast fall until after the animation has finished playing to avoid the longer landing lag. I would never, ever have found this if I just played with friends, kept to my style, and wasn't open to watching other sources of information.
Try to employ things you pick up on, hear about, or learn from other sources in training mode. Try to do these things first against a stationary computer, secondly against a computer that fights back, and, finally, against a real opponent. When you are able to find a friend to play with for hours of matches, make a very deliberate effort to employ techniques you're trying to master or add to your play, even if it hinders your performance or makes you lose. This is super important, as this is the only way you'll enrich your playstyle with improvements. I have entire play sessions where all I do is try to alter and improve my playstyle by breaking bad habits, adding new, good habits I'm uncomfortable with, trying new moves, trying to practice new techs, or just try other new things that typically end up making me mess up, die, lose, or do worse than normal because I'm not used to it.
An example of this is, I have a friend that plays King Krool a lot. I've been, lately, practicing approaching projectile-heavy, campy characters when I play him. I'll practice parrying his crown, his cannon balls, walking up to him through it with shield parries, and often I mess up and get continuously hit doing it. I choose this option over my comfortable option of jumping over everything, just for the sole purpose of practicing this kind of movement.