It will be at least months before SMTs are ready (I don't know the schedule for communities) and even then will likely be additional months or years if ever before any SMT becomes large and valuable enough for such a test to be meaningful at all, and even then it won't be clear whether such results would scale up to the entire Steem platform. For the foreseeable future the primary concentration of value on Steem will be the STEEM token and therefore the native Steem reward pool will be the primary motivator of voting behavior.

Honestly, SMTs and communities were a bit of a scam sold to us by Steemit as being something that: a) going to be was finished in a reasonable time, b) would instantly power all sorts of large and valuable projects which don't currently exist, and c) would successfully compete with countless other existing and in-development token systems in the blockchain world. Maybe (b) and (c) would have had a better chance had (a) actually occurred, but it didn't.

To be clear I think SMTs and communities are fine and I'll welcome them when the come but they aren't even close to a panacea to solve all of Steem's problems the way many seem to suggest (nor do we have even the remotest idea when they will actually exist).

takes so long to implement changes?

There are efforts under way to attempt to improve this as well. We'll see. But I'm not in favor of putting all eggs in the SMT basket for sure. I'd rather take advantage of all of the available opportunties to try to move forward.