I'm not a member of the WRM, PLA, NCRYM GGRM or FRRHS but I've visited all but Portola and supported them by buying a ticket or paying for admission so I believe I can offer an unbiased assessment of the situation.
It seems that all of these groups started out with good intentions of acquiring land, right of way and rolling stock to preserve them for future generations. Unfortunately they never have enough money to restore everything including the entire right of way so the paid employees and board members have to make hard choices choosing what to save and what to sell trade or scrap in addition to insuring that everything is safe and meets the requirements of regulatory agencies.
Naturally that alienates some people who don't get funding for their pet projects and they get upset and leave or attempt to recall people or file lawsuits which takes money away from maintenance and restoration. All the rusting deteriorating cars and engines creates a bad impression for many visitors. Its a lose lose situation. People who belong to these groups should realize most visitors are not hard core rail fans. They're happy to take themselves and their kids on a short (usually less than an hour) moderately priced train or trolley ride so they can experience the sights and sounds of a long gone era and maybe buy something at a gift shop. They don't expect or have time to see an example of every engine and car ever built. So don't be so harsh on the people who keep the museums going. Without them the museums would cease to exist.