When it comes to writing I don't think anyone should ever stop looking for ways to improve and grow their skills. There's nothing wrong with achieving a skill level and style that you're happy with but there are so many more things out there it would be a shame to ever stop searching or hunting after new knowledge entirely!
Unfortunately, from my experience, improving in any facet of life requires practice and lots of it. Though I suppose if you're interested in what you want to improve on then it's quite fortunate as you get to keep doing it over and over again. Practice, however, should not be meant to be a chore if that's not what you're interested in. It can be as simple as just continuing to write at a casual pace, or doing your best to write something small once a day every other day of the week. Either way, do something long enough and you'll figure out shortcuts and it'll become more instinctual.
Other than practice (because everyone says 'just practice' and even if it is true it gets old very quickly, trust me I know) I know that reading helped me immensely in growing my writing and language skills in general. It's amazing how much you absorb without even really realising it. If you can find an author whose writing voice really speaks to you I'd recommend that. Though a pitfall which I blissfully walked into as a kid was that I'd end up copying the writing style to a T and it very quickly stopped sounding like me. It was good and still reads decently even now, but it wasn't mine.
On detailing, I'd recommend thinking not only about sight (arguably the most predominant of the five senses) but about the other four senses as well. There's nothing that quite sets a mood like the sickly sweet smell of decay, almost seeming to settle thick on the tongue before the characters turn the corner and discover the not so long forgotten pile of decomposing corpses. Or the lukewarm caress of water over bare skin that leaves toes and fingertips pruned and hair damp, clinging limply to the back of a neck and causing bone-deep shivers when it gets cold.
Using senses other than sight in describing a scene can bring the reader a little further into the world which is always a good thing.
Characters is a more difficult one because of how broad the range of character possibilities is that you could potentially use. I suppose my recommendation would be to broaden horizons with what characters you create. If you typically go for a Lawful/Good hero type maybe try a Chaotic/Neutral villain, or something 'villain' adjacent (using those terms loosely of course, moral shades of gray are where I'm at). Popular kid that everyone likes - misfit that tries their best but never seems to get it right. You don't have to personally like or want to be friends with every character that you create. I'd say just that there really is no wrong way to make a character, but I think I would be very quickly proven wrong ha ha.
As to finding and utilizing different ideas in storytelling;
Something that I've tried - though it has primarily been in personal writing rather than RP - is re-writing scenes with a variety of different results/responses to a question or problem. As an example, say that your partner (if we're taking RP here) has just responded with their character confronting yours about something serious. If the first instinct is for your character to spin an elaborate lie, take the time to think about what it would be like and what they would say/do if they chose to instead tell the truth, or if they turned and ran, or if some other character was to walk in in that moment and interrupt what was supposed to be a private talk. Even if you know it's your character's nature to lie and that's what they're going to do, expanding your thoughts to encompass all possible outcomes can sometimes lead to more creative if not at least interesting adventures.
I've also done this with different character perspectives, to see if a scene is better told through the experiences of one person rather than another (again, in personal writing rather than RP). Usually, my first choice is what I go with but it's a fun exercise nonetheless, not to mention that it can help expand character knowing how they react to the situation personally rather than through someone else's eyes.
I tried to keep this brief but it got long anway, ha. In any case, my apologies if you consider any of this to be far beneath your skill level, offensive and/or completely useless, but hopefully it will be of help to someone.
