interesting question whether all changes are only chumros and gezeiros …
first, “greater beis din” was less of the issue in antiquity, as such things happened…
not sure whether conditional get by Dovid was a change or not
allowing moabite women – if not a kula, at least a clarification
– changes in school systems and ketuba during BM2 – not really kulos or chumros, just changes searching for successful social results.
– shemen akum – was announced and taken back within a year because people did not accept it.
– writing down Oral Torah
– all post-BM2 changes
– allowing taking money for teaching or even learning Torah and probably other things that are allowed because “our generations are weaker”