Not true. If we marketed it as "Fire Monopoly" we would be infringing on their trademark. "Fire-Opoly" does not infringe as long as nothing is exactly the same. You cannot use the word "Monopoly", and the rules cannot be copied verbatim from a Hasbro copyrighted work.
For example, the "Community Chest" & "Chance" cards could be changed to, "In-Quarters" & "On the Scene", etc.
And if you want to penalize another player you could buy a burnt out house to place on their property and they would have to pay to get rid of it. And if they don’t get rid of it before someone lands on that property the owner of the property has to pay a fine to the person who landed there and the person who put the burnt out house there in the first place.