If you've opened a Premiere Pro Template and you get the following "Upgrade Legacy Titles" prompt - don't worry, you can still use these titles!
Legacy titles can be edited from the Render sequence, by selecting the Text layer in any given title render sequence, and then by double clicking on the title in the preview window to edit. This will also activate the text tool.
Legacy titles in Premiere Pro 2023 can also be edited from the Essential Graphics window (go to Window > Essential Graphics), then select the title in question.
Legacy titles in Premiere Pro 2023 can also be edited from the Text > Graphics window which is accessible when double-clicking on a Legacy title from a sequence.