Hi sigafoo, I wanted to give my input as a spectator. While I don't play competitive TF2, I've watched HL, RGL, and 6s, and I find both competitive TF2 and the community very interesting. I did attempt to get into competitive TF2 a long time ago, however; one of my friends introduced me to Highlander, where I decided to try out engineer and stumbled upon videos of your gameplay, which I enjoyed. Eventually, though, I realized that what I liked about TF2 compared to other games was the fast-paced, DM-heavy style, which I couldn't play as engineer, so I looked into 6s scout instead.
That brings me to my opinion on what makes TF2 fun to watch: the very same fast-paced game with mechanical skill that I liked to play. Can a roamer bomb in and get a clean shot on the medic with an airshot to finish them off? Can a scout finish off the weakened enemy team after most of their team is dead? These thoughts make the game interesting to spectate, especially with an offensive team, or when much is on the line like the Australians in the Insomnia series.
I admire the work you're putting into RGL by dropping your own money into it and casting the matches, but personally, I don't like watching it. With 14 players, it's just too difficult for one individual player to shine (or even kept track of in the first place). There's less full wipes, more pyros and engis (which I find uninteresting to watch), and (while this isn't a problem with the gamemode itself) no high stakes or rivalries.
I think the pick/ban format is a hot topic, and what I'm thinking is that it can be interesting to leave powerful weapons in specifically to see how the teams take advantage of it. I'm assuming your view is similar, because there aren't enough bans to get rid of particularly powerful unlocks (Bonk, Natascha, Wrangler, etc.), but please correct me if I'm wrong. However, when these powerful items are ones that encourage stalemates rather than aggression, taking advantage of it just makes the game unfun to watch.
All of that said, I don't think it's wrong that you've put some money into your league. It's unlikely that someone has stopped playing 6s or HL because of 7v7, unless they didn't enjoy 6s/HL in the first place, so I don't think it's fragmenting the community compared to the ESEA vs CEVO fiasco. But I think there's lots of improvement to be desired for RGL to be spectator-friendly, and I don't think it's much of a strategic gamemode.