Then when they die and the house gets sold/transferred at a value of $1M the property taxes are going to skyrocket 5000%

In what jurisdiction? Where I live, the city re-calculates the assessed value and bumps up the property taxes annually.

Inheritance is irrelevant in an abundance-society.

Really? I’d think that if mom and dad owned a 180,000 acre ranch and water rights, inheritance will be very relevant to their only child.