I think the only things that prevent me from giving a 4,5-5 stars are the seriously insufficient tutorial and baaaaad user interface. Aside from that, however, if you take the time to learn the game and understand it's a board game adaptation, it's absolutely fantastic. Performance issues can occasionally happen but this isn't a game you play for looks.
Both halves of the game - classic Baldur's Gate-esque DnD, and the kingdom management sim sound great on paper, but get entirely crippled by one or two awful design decision that ruin everything that makes them fun. I'll start with the party DnD because it's significantly better: The critically bad decision was to make the DnD part a resource management situation due to the retsing mechanic using up heavily limited resources and time. That means you can never use your powerful party to their full extent against proper brutal enemy encounters. Instead, you're managing every spell cast and hoping you'll last until the end of the current dungeon. That also makes it that no encounters are particularly challenging unless you bastardize the difficulty sliders, and you're just fighting numerous encounters of the same mid-tier, unremarkable slush. And the kingdom management is straight up one star, a massive ball and chain on your leg, unexplained, ramping up in difficulty to the skies, with zero actual reward for it. Thankfully, it can be disabled.
As stated elsewhere, GOG includes the patched version getting rid of most gamebreaking bugs and unfinishable dungeons. However, it stil needs some TLC to run decently on Windows 10 - grab dxVoodoo patches for graphics and patches for menu performance. However, that's fine. Once the game is set up, it's real fun. Until I got to the unbearably stupid promotion quest system where you have to select characters BEFORE finishing taking the promotion quest. If you didn't do that, you're completely locked out of that promotion path, which lost me some 20-ish hours, because I just took the quests to do them and submit them later. After this, I really didn't have the strength to restart. Now, I might return to MM9 at later date, but after finishing 6,7,8 in a row, I just remembered the disappointment from when I was young and finished the game the first time. I'm giving 3* because the game IS fun once set up, but the frustration with some INCREDIBLY stupid design choices drains all the enjoyment out of it.