Remember: design for social media is only an accompaniment to the meaning. It shouldn't overshadow all the attention, no matter how long or inspired you work on your visuals. Beautiful doesn't always mean complicated.
The niche is the same, but the mood is different.
Beautiful is harmonious. Harmonious with the text, mood, audience, and product. It's difficult to find this harmony. There's only one piece of advice here: practice a lot with new challenges, diverse niches, and target audiences. Observe more, get inspired, and repeat (but don't copy!). And don't forget: social media design is just a part of web design, so you should start from there (just a little hint for you) ;))