It’s not exactly an AMA or a Q&A of substantial length, considering Riot cherry-picked questions that tied to an overall topic, but League of Legends has indeed answered some questions about what it plans to do about game modes and events in the near future.
Feedback about events feeling generally low-quality has been heard, and the LoL team is working on making events “more rewarding, more novel, and more memorable for everyone.” This means bringing back new and old game modes to events, introducing a reward progress bar that fills whenever you take on event missions, and making missions more varied overall. These adjustments are due soon with the incoming event celebrating the 2019 World Championship.
Speaking of game modes, the post offered a brief update on the Clash rework, noting that things are now at the regional testing phase. The new Clash mode has been tested in Turkey, LATAM South, and NA so far, but more regions are tentatively scheduled to be included in weekend testing between now and mid-October. Emphasis on tentatively.
Finally, there’s a quick note on why Ultra Rapid Fire and other game modes aren’t allowed in custom matches. Simply put, some of these modes can be so buggy that using them would crash game servers, which is not a risk that the LoL devs are willing to take.