That is absolutely what it is…
That is how MiaB is configured out of the box, yes … but that does not mean that it has to be used that way. It was created so that someone could host email AND a simple static web page. There is absolutely no reason whatsoever that it will ‘create websites and take over managing their DNS’ if you do not allow it to. As a matter of fact it can only host simple static websites, so for many it is not sufficient to be used for web hosting. Again, there is nothing saying that you have to.
It is ABSOLUTELY suitable to the task that you defined:
How possibly are you imagining that it isn’t??? It checks all of the boxes for you.
- A separate mail server
- Ability to set up a webserver on another VPS
- A turnkey solution to mail.
I can only IMAGINE that you DO NOT understand how things work to make what you want to happen a reality. To understand these things takes a bit of reading and research on the issues you have presented which seem to be:
1- That is hosts websites … no problem, host them elsewhere.
2- That it manages DNS … no problem either set the custom A records for your websites in the custom DNS section of the admin area OR manage your DNS elsewhere such as the domain registrar or Cloudflare.
I simply do not understand your issue here as MiaB DOES EVERYTHING YOU DESIRE. You just have to understand how DNS and the internet work.