@afewbugs There's one thing that I can somewhat, only a bit, accept as an excuse for talking about NextCloud in particular: It operates on CalDAV Standards and the Tasks part of that ... sucks badly. Like, terrible. I've not been happy with any of CalDAV synced Tasks because not only is support shoddy, but for exactly the reason you give.
However, NextCloud could – as any one of the stakeholders – try to push for something different or find ways to enable this use case better.
Case in point: What do people use for such tasks? Alarms are... hard to manage. Calendar entries are overwhelming. I try paper but I forget too often.