I'm a dev who has moved more to lead dev role, and for the record I've predominantly used SQL Server for all data storage.

For the types of projects I work on anything with out a defined schema = NO! Customers want to be able to create their own reports and as soon as you need to do that then storing arbitrary things like JSON that could represent anything immediately makes this a nightmare. And maintaining one store for JSON etc.. and one for some deserialized versus in a relational database seems like something that is doomed to cause nothing but headaches for all involved.