(Double reply, evil i know)
I really gotta emphasize that the 6 FW is literally just a prettified 512/510/509. There's nothing really interesting to it. The only thing that really changes infra-wise is the double point switches, no turnback loops, and standard gauge. The rest is fluff. Off-board payment, level boarding, nicer signage... And unsurprisingly, the 6 performs on par, speed wise, as the 512/510/509, because that's it. That's the only changes.
But due to its LIGHT RAIL designation, 6 FW was mentally put on a higher standard than the rest. It was supposed to be faster. The 512/510/509 is slow due to infra and switches or whatever, or the 1000 other reasons the TTC trots out. The 6 FW was supposed to fix all the infra problems- which they did- and when all the infra problems were solved, it revealed that it was just the TTC being horrible at operations.
Left alone, the TTC has only made the streetcars slower on dedicated ROW routes. Left alone, the 6 FW will only get slower. The public, province, MX, and city need to kick TTC into high gear. Other agencies would operate this exact same line at 20+kmh avg, as has been shown in this thread.