at the end of the day the message is: it is impossible to connect legacy and wifiwave2 CAPs to one CAPsManager. is that correct?`
Yes, this is correct and they never made a secret about it.
This was known from day 1 capsman for wifiwave2 came out.
Sorry, that is a really bad policy by mikrotik and it is worth to think over using mikrotik at all. the big advantage using mikrotik is gone.... sorry.
We are not using a steam engine as main motor anymore either for most applications, do we ?
One day or the other Mikrotik HAD to move away from legacy wifi.
The launch of AX devices opened that door. But all AX devices (and AC3 which can be upgraded to wifiwave2) use one single version of capsman controller.
So that argument about 1 controller still holds if you make abstraction between legacy and wifiwave2 devices.
You still CAN use TWO capsman controllers within the same network during transition.
One for legacy wifi devices, one for wifiwave2 devices.
You do not HAVE to change everything at once (but personally I would consider it given wifiwave2 under capsman control is quite a bit better then legacy wifi capsman environment, my view).