Just to chime in with data here, there is 5x more feedback per day on the new system than there was with the old system. Depending on the track, you'll get feedback in 3hrs to 7days (very occasionally longer), so it is definitely inconsistent in that respect, but you will get feedback. In the old system, you'd get feedback at all in under 10% of submissions.
> There was one mentor that I would have happily paid directly to keep giving me feedback, but there was no mechanism in exercism for me to make that offer, even if exercism took a cut.
In the future we'll be adding the ability to "pair" mentor/mentees who have both rated the other highly, so this will sort-of happen for you.