You seem to be quite frustrated with the comments already in the post... you don't have to read them
I bought into the R system 3 years ago precisely for the mirrorless advantages including new RF lenses and the ability to adapt my existing EF lenses (which I still do). There have been a lot of RF lenses released since I got my R5 but the key ones for me at the time was a lighter/smaller RF70-200/2.8 and the RF100-500mm.
In essence, the combined EF/RF and adapted 3rd party EF lenses suit most of my photographic wants. There will always be gaps though. We would like to think that Canon could fill those gaps especially as I anticipate further (complete?) discontinuation of EF lenses. We are only 5 years into a mount replacement so relatively early days but a couple of gaps seem to be obvious which Canon may or may not want to cover:
- RF50/1.4 => massive gap in price and optics between the RF50/1.2 and RF50/1.8. The Sigma EF50/1.4 Art is an option though
- No wide RF-S lenses => no APS-C body can do wide angle without adapting EF-S wide angle zooms. My EF-S 11-22mm was my second lens I bought for landscape with my 7D but until either a repackaged EF-M or EF-S lens is released then this is a gap
- Specialist RF replacements for TS-E, MP-E, long macro, fish-eye haven't arrived yet. Definitely niche products but discontinuing EF mount versions is intriguing if there is no replacement
- Niches that Canon has not tried to enter with EF lenses were covered with 3rd party eg fast/wide primes especially for astro landscape with low coma. This is a little strange as Canon has had multiple modified filter bodies for Ha sensitity available for a very long time but nothing since the discontinued Ra body.
Some people can justify or afford multiple systems (body / lens) for a specific purpose but there are downsides as well. Always best for the user if they can get everything in one system but we know that won't happen.