Meshtools in Rhino like booleans, trimming and splitting have always
been broken. In my opinion they are of such poor quality, they are best
avoided.
I sometimes read harsh statements like this, which I can understand there are some things that drive me nuts too, but for me these are not so much on the mesh side of things. For Rhino being a NURBS modeller and a tool with a very wide scope I was still delighted to see the improvements in the Mesh tools from v3 to v4. I agree the advancement since then has not been progressing very fast, but still I mesh booled this STL model with +4000 intersection into a single closed mesh for stl printing back then, using the 4.0 WIP. So saying they a broken is not right imho.
Of course things could be much better and I hope they will be soon, with work being done in the sub-D area too.
but for companies doing time/project critical work on meshes often, the investment into something like magics can be a fast turnaround, such software is very expensive, for a reason.
