Nothing will change as long as builders are not allowed to build a 3 family on a 5000 sf lot.

There are lots of towns in Maine where you could do that if only zoning allowed it. Wherever there are stores, that’s where you could have such zoning. That would instantly increase the value of a single family sitting on a 20000 sf lot in the town center. There’s no need for a house in the town center to be sitting on such a large lot. Change the zoning, raise assessed values to reflect highest and best use, and such owners will voluntarily subdivide their lots and sell them just to lower their taxes. Builders will buy up those lots, build multi families on them and new buyers will have rental income to support their mortgages. Multi families on small lots won’t appeal to buyers of short term rental vacation type properties.