75 years is something like ~3 human generation.
3 whole generations that don’t get to decide how to govern themselves because their grandparents signed away their future in an iron clad contract.
I work with a nonprofit that is negotiating a (standard length) 75 year lease for a piece of parkland. The nonprofit will have to invest many millions of dollars into buildings and improvements on this land (all publicly accessible). Without the 75 year lease, there is no way the nonprofit could run a capital campaign to raise money for the improvements - nobody would be willing to donate money if in a couple years the government could choose to change their minds and rip up the contract. This type of dynamic exists (someone else needs to make a huge upfront capital expenditure, and they need some sort of guarantee that they won't get "rug pulled") all over the place.
Case in point, in 2017 Austin leased part of the airport for another company to run as the "South Austin Terminal". The original lease was for 40 years, and then only a couple years later the city changed their mind and decided they wanted that land back to do a major overhaul of the airport, and they tried to get it back with some extremely shady eminent domain tactics (and they basically got their ass handed to them in court). I actually hate the South Terminal (it's confusing and not connected in any way to the major Austin airport), I'm glad to see it go, but I'm also glad the city can't weasel their way out of a bad decision just because they changed their mind: https://communityimpact.com/austin/cedar-park-leander/transp...
I agree that there needs to be some way to hold previous office holders accountable for decisions that affect a locale long after the original signers are gone, but just saying we can only have leases for 20 years or so isn't the right way to do it.
if you keep protected areas within control of the government, there's always a concern that the next government decides to cancel those protections and sell that park off to industry or development. but if it's already "sold off" to a non-profit who wants to keep it a park, then it can't be sold to industry.
But I think the underlying point is that maybe we just shouldn't do that? Our governments should be able to competently administer things like parkland and street parking. And the cost of giving up on them doing that is unacceptable because as you say, you can't do it without giving up control for an intolerable length of time. So sure it's necessary to do that if you're gonna do it, but that's precisely why you absolutely shouldn't do it, it's an absolute dereliction of duty.
While your typical playground makes sense for the city to administer, if the park is really a zoo it makes more sense for the city to not run it at all. However since the city benefits from the zoo it does make sense for the city to help the private zoo get started in a good location.
Point being that municipal governments have tons of responsibilities: airports, parks, health districts, roads/sidewalks, etc., etc. There is just no way they can be competent in all these different areas, and indeed they aren't. There are good examples of non-profits that manage public resources much better than city government can, at a much lower cost (the Trail Foundation in Austin comes to mind for me). We shouldn't throw away the baby with the bathwater.