GeorgV | Thank you for your thoughts and asks. I will pass along the value of continuing to improve Lookups. The focus has been to tackle the 70-80% use cases/columns, and we know we've not completed all that could be included - esp. for mature use/expectations of Lists. We, too, are looking at how templates could bring content in initially, and the ability to add news content in bulk fashion to an existing list.
Specific to template management, I'll pass along your feedback to the team. For now, I know we have these docs if you've not come across them: https://learn.microsoft.com/sharepoint/lists-custom-template. If in your review of this documentation, you find ways we can improve and make it clearer - I can pass along your insights to our content design team.
I, too, will nudge our Lists leads to review the Feedback Portal space more closely/often: https://aka.ms/Feedback/Lists
Again, appreciate you sharing here, Mark Cc LincolnDeMaris Miceile Barrett