Markets are fundamentally about choice and trade offs. Monopoly is about runaway power dynamics created through random chance and force (you have to pay rent, you can’t choose not too).
1. you cannot increase the supply of property, or build something bigger than a hotel
2. rents are rules. You cannot be creative with rents. I.e. rent control
3. there are no predictable expenses to owning property
4. the only business you can engage in is property
5. there is no supply & demand at work
6. what properties you acquire is completely random
7. the outcome of the game is controlled by a roll of the dice. There is a strategy to Monopoly, but it is very simple, and soon everyone learns it and that ceases to be a choice
8. Not being able to collect rents on mortgaged properties is quite unlike any actual business
9. No interest is paid on debt
The biggest divergence from an actual marketplace is it is designed to be zero-sum. Markets are not zero-sum.