Templates are an often-requested feature that is in the developer’s plans, but not in the short term.
I haven’t used Obsidian; maybe it has a different mode of use than Legend. I have always thought of templates as a “starting point” for creating documents – perhaps with custom formatting to go with it – but once that’s kicked off the document is yours and the template is not “active”. Your description of “templates” sounds more like inserting preset “snippets” that you use in individual items or notes. That seems like something you could handle with a “text expander” utility. Some text expanders have the <date> functionality you describe.
Legend currently tracks created, modified, and completed item-dates, although this information isn’t super-visible. RMB on an item and look at the bottom of the popup to read these dates. You can also configure Panes to group/sort items by the created/modified/complete dates, but honestly those Panetypes need some refinement.