Welcome!
There will come a time when the tool that you require for a job is just not sold, such as a form tool of some description. Or such a tool is available but too costly to justify buying for a "one off", never to be repeated job.
(Cutting a 14 mm internal thread, for instance, springs to my mind. Larger than the Taps that we usually have, but too small for many metric carbide insert tools to enter.)
Under those circumstances the ability to grind your own special in HSS is invaluable.
HSS is economic, also. Carbides chip more easily, so one careless move costs you £3-4. Ditto with HSS means five minutes on the grinder, with lots of the HSS toolbit (That cost the same as one insert ) still left. And the grinder is always available at 8:00 pm on a Saturday night, after having chipped the last insert!
Personally, for most turning work I use a Tangential Turning Tool. It does what I want, and is easy to sharpen, (Only one face to grind, using a small jig )
But for certain jobs, (Boring is one ) I use carbide inserts Horses for courses.
Certainly, make / buy a rear toolpost. This is very useful for parting off, and generally causes far fewer problems than parting off in the front toolpost. Why? Don't know. There have been lots of explanations of how the reversal of the cutting forces improve stability and rigidity. The essential thing is that it works. When I had a ML7, I made one and never looked back for parting off.
As an aside, for the larger machine that replaced it, I made a four way indexing toolpost, like the front one, carrying front and back chamfer tools as well as the parting tool.
The parting tool is the same one that I was given for the ML7 back in the late 70s , and still just less than half used!
HTH
Howard