Very few database systems support online DDL, which unlike a transaction, does not require undo or rollback resources. Of course one must have a rollback procedure if something fails, but you need one for transactions too, just in case.
An online rollback is far lest costly than a transactional rollback, because and online rollback is just undoing what you did. Added a column you didn't want in one query? Remove it again in another, very quickly.
TokuDB (a mysql/mariadb storage engine) supported all DDL as an online operation. But percona killed it in favour of TokuMX, the MongoDB equivalent.
TokuMX has no upgrade path to wired tiger, only one major customer at Percona (I can't say who it is) and no engineers.
Any kind of DDL is tricky and requires users to RTFM for the intricacies of their chosen database. One size rarely fits all.