Regarding the avg time on page for custom reports, I made a change request to Innocraft about that 2 years ago. I suggest more people do the same and it will hopefully be prioritized.
I think this type of question is really about selecting a professional Matomo provider.
You local IT department is usually not a good choice in this case.
Sorry joking a bit there ;) what i mean is that Matomo is a very complex tool and it is great that we can adopt it for different needs.
However when you offer Matomo to others, you should know these details and of course configure it with the setting above enabled as an example.
Regarding consent management, I would like to add that it would be nice if it could possible to process consent to geolocation with a full IP address. Currently this is not possible.
The limitations are mostly about Matomo is a relational database, this works well for small sites but when data grows the queries gets heavier from a tech perspective in some cases. Then the need for super skilled dbas are needed.
Yes, the database is often the "brake" for fast response times. This is also my experience with sites that have stored the data for many or many years.