Just posting because OP getting fired up over an RP having standards is hilarious. 

Real talk though, you're not going to fit the wants and needs of every GM neatly inside of 3 sections. Honest bullet points for all the sections would look something like this:

Free: For people who don't take the writing aspect of RPing too seriously and prefer a fast post pace.

Casual: For Free roleplayers who don't mind reading longer posts, and Advanced roleplayers who don't mind reading less-than-perfect writing.

Advanced: For people who want to challenge themselves, take the writing aspect very seriously, and/or prefer a slower posting pace.