Limits can be rendered, they’re just inline(see Writing Limits in CL)
A more fulsome answer to this is that Desmos uses Mathquill under the hood. Mathquill itself has a Pull Request on its Github page going back several years for this particular issue with rendering limits as inline rather than {Displaytext}. I’d suggest either asking @JayChow or @eric to submit a PR there or to speak with Mathquill about improving this.
That said I believe Desmos itself uses a limited(no pun intended) version of Mathquill, so perhaps the general situation could be improved on the Desmos side of things.
I know there is a general need for better, more robust handling of things such as \cases for piecewise functions and whatnot, so improvements in this area would be most welcome.