"Several users have reported to me that they too have experienced serious problems with Time Machine in 10.15.3, both in making first full backups and in trying to restore from existing backups. At least one of these has been reported to Apple as a bug in Time Machine, and has apparently joined several previous reports of the same problem." (My emphasis)
Clearly there are people who have what I'd call serious bugs, including people in the comments here. But it doesn't seem to me like anyone has proved that there are replicable serious bugs with Time Machine - although of course just because it's unproved doesn't mean it's not the case, and two backup methods are clearly better than one.
I've never had an issue with Time Machine (touch wood) and have found the ability to easily revert to previous versions a godsend sometimes.