They did do it right twice, back to back in fact. I can't speak for pre onslaught blocks though.
One of those is Ravnica which they couldn't even recapture the three-set magic on a second time (instead producing one of the absolute
worst examples of Third Set Syndrome ever) and the other is Time Spiral which still has a jank set (Planar Chaos) and was such a business disaster that it makes their Top 5 "Things We Won't Do Again" list.
I didn't invent it. The pace feels overwhelming to me right now., mechanics are getting 1 set to shine then being discarded (see: Investigate, that Convoke for Artifacts mechanic, etc.) and it just generally feels like the brakes need to be put on in some form.
I agree that this pace was awful, but they haven't until
probably now with Amonkhet actually given the most obvious solution a shot: cap blocks to 3 mechanics in the big set and one added in the small one, then just make sure the ones you're adding actually pull their weight. If Kaladesh was the high end of mechanics instead of the low end you'd see a higher hit rate on individual mechanics (three of the five in KLD block are major Constructed players and one other clearly pulls its weight in limited) and a much less muddled picture overall.
What's wrong with them going back to to 3 sets per block?
The core problems with three set blocks were basically as follows:
- Almost no theme actually has enough material to stretch out to three blocks, nor do most mechanics.
- Players are already used to the environment seven months in, so they don't care about your marketing messages or the set reveal much and need a huge change to actually be impressed.
- But doing a big swerve in the third set involves either a mechanical reboot or a confusing and disruptive level of change within the block.
- All of that results in a third-set problem, where the last set is underwhelming, unpopular, and called out as "bad." (Sometimes they'd load up the third set with something interesting and they'd have a second-set problem instead.)
- The story is the single biggest monetary driver of new business WotC has had in years, and they basically can't tell it at a rate that keeps people engaged if they have to spend an entire calendar year on each world.
- Meanwhile, because core sets had no unique flavor or distinct selling points, and were half reprints, people didn't care about them or buy them much.
(I might've forgotten something here.)
how are they burning through worlds? ever since the changes we've had 2 returns and 2 new planes.
Yeah, the thing to do here again isn't to slow down block production, but to just tilt further in the direction of returns and start treating core worlds as a stable of primary settings. The first time back to a plane it makes sense to make a big deal of recreating the original block with a twist, but if you need to slow down creation of new settings just do 3+ returns of popular worlds where you don't stick as closely to the exact format of the original.