Cookie banners aren't a requirement unless you wish to store cookies that aren't strictly necessary (statistics, marketing, etc)[0]. Cookies that are essential for the user to browse the site (login tokens) don't require consent.
It doesn't help the situation that a large number of sites seem to maliciously comply with these regulations.
So if I use telemetry to catch some dirty frontend blob throwing a hissy fit of an exception and that telemetry is tracking sessions rather than individual events (hello ms app insights) -- is that functional or, statistics or etc?
To be completely sure, you should eliminate anything that might be considered PII.
So unadorned exception counts would be anonymous, aggregated statistics, which is fine. But exception counts reports per IP address, or per session, or where the exception text mentioned the user's PII, would require consent from the user you're tracking by processing that data about them.
Non targeted ads pay 90+% less than targeted. Sure it's not 'required', but the vast majority of businesses would fail overnight if their revenue dropped 90%.