Having instant access to either blue or black mana makes early turns much smoother, whether youre holding up interaction or trying to land a key engine piece
The temptation to add a Renegade Map is a strong one, but the ability kind of runs contrary to what we want to do: it enters tapped, and it replaces itself with a land, which is basically only a small upgrade in an improvise-heavy list
If you also attack with Phyrexian Dragon Engine, you still trigger Mishras attacking trigger, but then meld the two
Being able to escape this is a nice touch, so I could see it slot into decks that are filling their graveyard and never want to leave mana unused, but its hard to see this doing all too much in most decks
And let me tell you, when the Muldrotha train gets rolling it doesnt stop