I think most people in the English-speaking world get an idea beaten into them during their education: that you should write in short, to-the-point sentences that have a very regular and clear structure.
But here's the thing, go read any piece of text that you consider lush and evocative, especially in a texty video game context, and just... pay attention to how much punctuation is there, how often there are subclauses or irregular breaks (em dashes, etc), how often there's grammatical oddities like funky tenses. It's usually a lot!
This doesn't just go for your Fallen Londons and Disco Elysii, either. Look at any game that has a lot of short dialogue without VO, like Animal Crossing. You'll see heavy use of ellipsis, big variations in style from different characters, odd or irregular sentence structures. Lots of little ways of building interest and voice. You can do it without walls of text; you can do it at a grade school reading level.
Also: try transcribing how you talk some time! You will soon discover that you have so, so, so many run-on sentences, and it's fine.
Short, punchy sentences are for informational delivery. They create small, digestible pieces of information. This is important for specific kinds of writing. For everything else, go nuts~
In support: something I have to tell text-based roleplayers (I DM and play in a few text-only games, along with some jaunts into FF14 RP) is that they SHOULD take some time and feel free to write small, punchy sentences, because a lot of them really do like florid run-on sentences, taking 3, 4 paragraphs to say "hi". Sometimes it's okay to just go "Hm! I heard that the vizier was banished, though. Is this true?" and leave it at that.
Basically all of the above is 100% true and one should not discard useful tools, or feel that they're cheated when someone responds with brief but thoughtful bits!
Brief, solid sentences are bricks. Foundational structural pieces of writing. Fragments implying that kind of structure are cinder blocks, also structural but you don't want to show too many of them or it looks ugly. Explanatory parenthetical commas like the preceding are doors giving access to the structure of meaning. When sentences get more involved -- em dashes, lists, and other things with elaborate punctuation -- they're more like windows; you get a view of something inside, more or less interesting depending on the structure and content and context.
Making words do things is an art. There isn't one way to get it right. There are many ways. However, there are basics to understand before breaking the rules of thumb, or else results can be erratic. Some things are wrong most of the time but occasionally right!
On the flip side those short sentences fo have a use beyond being functional and direct. They can be quick and kinetic. Cutting away description, winnowing down extreneous information, is a good way to convey speed and action.
Like anything knowing when to use these tools is a matter of experience. Write often and don't be afraid to do things outside of your norm. Similarly reading and reading from a wide variety of genres will expose you to different techniques and teach you accepted practice, even if you go ahead and break those rules later.