Hi Roman,
Ok great, you're at least also of the opinion that bigger sites will need an actual implementation. I want to make sure to at least mention these articles too, to not give people the idea that they should all go ahead to implement it through GTM, as it's still not a recommended way to go:
- https://www.upbuild.io/blog/dont-use-gtm-for-structured-data/
- http://www.thesempost.com/google-dont-rely-google-tag-manager-structured-data/
- https://www.seroundtable.com/google-google-tag-manager-seo-24984.html (see the Tweets mentioned in this article, it's based on John Muellers reply to my Tweet about all the down sides of implementing GTM for structured data).