It's based on the current view by a few folks (not bothered to go dig names up) on the board re we shouldn't play a DM (I think you share that view), despite the fact that from a system perspective some of the best recent Spurs teams have had a DM, i.e. with Palacios -> Parker -> Sandro. When brought up, the dismissal is somehow a pure DM can't play football, won't fit in Poch's system, etc, etc.
Its already been pointed out that with a DM we have lost a game (not sure what that proves), Manure has lost a few with Carrick and better players around him. It's about consistent performances from a defensive perspective (At this point I think we are conceding 2 goals a game for more than 10 games now).
We haven't replaced Carrick but my assumption is our DM & Eriksen setup would look more like a Sandro/Parker & Modric. I think it can work, and I think you can find a player that can do the role, and fit Poch's system. I don't pull out names of players I've never seen play outside of a game or two, so not good at the suggestions.
Its not a dig against Mason/Bentaleb, its a dig against the system that is slightly overbalanced with Mason/Bentaleb being more attacking focused, +two overcommitted FBs, +an unsettled/out of form CB pairing allowing too many goals. We either to your earlier point figure out how to press to the point where we don't let them get the time to make chances, or get at least one more defensively focused midfielder.
Even though Stambouli & Dembele are not as good as Mason/Bentaleb, I think Poch needs to figure out how to leverage them better, because the 2-1s & 4-3s can easily go the other way and 5th-7th is likely to be just a few points.