Seriously? Look at how the old EF lenses compare to newer lenses made for mirrorless, its not even close. Most are absolutely terrible. We just never noticed it shooting 12 megapixel DSLRs back in the day. Cant get away with that on 30-45 megapixel cameras with current sensors. Oh yea, just go grab an EF adapter for each of my EF lenses like they are free and growing on trees. You're joking right? These things have been out of stock for EIGHT MONTHS and when they do get stock, they are gone within minutes. You really think Canon can't produce these things and keep them in stock? Of course they can, they don't want to though, because they want you to spend big bucks on their absurdly priced RF lenses. Once again, it all goes back to Canon's greed.They are absolutely appealing! Not sure where your difficulty is. Canon has made the transition easy for those with existing glass (as I had and still have some).
Some lenses are old but a lot are younger then 20 years old especially for the alternatives to current RF lenses.
More EF lenses are available on the second hand market at an even cheaper price as well with people moving to RF.
If you don't like the adapter then pretend that it is welded on and have one for each EF lens. Yes, they can be hard to find in some markets but you asked for a mid range option and then complain that the mid range option is either an old design or that you have to spend USD100 for an adapter.
Using the ND/CPL adapter actually makes the filters cheaper eg for the 11-24mm/4 or EF8-15mm lens than for the external options.
I won't be getting the RF100mm macro or the RF14-35mm/4 lens because the adapted EF version are a great price and are great quality.
It will be a long time before the EF8-15mm/4 is available in RF so my second hand version is perfect for the limited times I use it.