Developers without special training should generally not do database design for the sort of databases that are intended to last decades. It is a similar task to developing a complex file format that is usable twenty years later - not something to be done off the cuff, and if you want schema stability database design requires more care than most file formats.
While I agree with you, unfortunately this is unrealistic. Unless a startup happens to have someone skilled with schema design, they’re going to make do with what they can, and it’s very unlikely that they’d waste headcount on a dedicated DBA / DBRE at a young stage.
The immediate effect of that, of course, is that they also won’t try to hire any such person until the DB is a problem they can’t scale via throwing money at it.
