Did you import as HTML or Markdown? The former will do a far more accurate rendition at the cost of making it harder to edit. The latter will use Joplin's "native" format but will lose some formatting due to limitations of Markdown itself.
If you are using the rich text editor rather than markdown then you need to ctrl+click it (possibly cmd+click on macOS?) as otherwise it wouldn't be easy to edit the text using your cursor. In a preview of the note it should be clickable like normal. This should be a similar metaphor as used in many word processor type applications.
This is coming in v3 - currently in pre-release
It is an open source project and yes, does probably tend to attract more people who are happier with markdown but I think saying that people who like Markdown aren't enthusiastic about note taking as much as others isn't a fair evaluation. I wouldn't be anywhere near as prolific or efficient in my notetaking without Markdown, using a richtext editor is just too slow and cumbersome for me.