As you can see, the only three instances synchronizing in more than 5 minutes are
reddthat, based in Australia
lemmy.nz, in New Zealand
aussie.zone, Australia too
feddit.ch, closing at the end of the month
For the 3 first instances, this is due to lag and centralization of communities on LW. Moving communities away from LW would actually help solving that issue (in parallel, Reddthat is planning to open an EU server to reduce the lag)