Metabones speedbooster: is there any reason to get full frame now?

You do not see ignorance. You are too quick to correct me and another poster here without even trying to understand what we say. You are basically arguing with yourself. Yes, adapters are a well-known technique. No, they cannot replace a well designed lens. For example, the 135L+1.4TX cannot reach the IQ of the 200/2.8.  See TDP, for example. The 200/2+1.4TX is not as good as the 300/2.8, etc.

Here, we have compression. Putting additional glass at the end of a great lens cannot remain unpunished.