That is why groups like the: III%, Cajun Navy, American Freedom Keepers, Highwaymen, Riders of the Confederacy -- go out in groups, set up a base of operations with a logistical support network, and generally have some training. Many of them are also ex military, ex police, ex medics, worked in logistics, and many of them are techs as well. They also usually have human intelligence on the ground before they get there, tend to make contact with law enforcement when they arrive so they know who they are so they don't freak out with a mess of guys in gear show up. You don't want people to mistake you for an armed group of looters! They try to connect with businesses and church people ahead of going. They tend to take multiple forms of communications gear, extra fuel, and whatever other resource they can with them that might not be available that they can carry.
That does not mean its always perfectly organized, pretty, free from chaos, nor that it is free from danger. If your area of operations is bacteria infested water, that alone is a danger. It does not mean you cannot end up a part of the problem even after successfully being a part of the solution. Especially if there is no logistical support available to you easily beyond what you can carry. Situations can change rapidly. A levee breaks or a river crests or a road is completely washed out after you get in. Stuff happens. I've seen some of these groups do some pretty amazing things with what they have to work with. Sometimes that is the only support that will exist.
An example of that danger from Hurricane Harvey is where several people took the only good option available when effecting a rescue or bringing in supplies would otherwise have to be brought in by air -- the monster truck or 5 tons with very high intakes and exhausts. These could get into areas that boats could not, and other vehicles definitely could not. They were even in areas that helicopters would be useless in. However, wheels have wheel bearings. They don't perfectly seal. At best they can be packed with grease to keep some of the mud and cruddy water out. After a few days of operating these in that water while sometimes carrying in heavy loads of supplies and ferrying people out, they literally drove them until the wheels came off. The issue of logistical support being unavailable put at least one of them in a bad situation. They did way more good than bad, but not having that support when the rest of society is washing away down the river is never a good thing, especially when the waters are rising all around you and you cannot effect a roadside repair.
All of that being said: A lot of rescue, national guard and support organizations simply bypassed the smaller towns leaving them to fend on their own. The militias and other groups saved a lot of people, coordinated their own usually completely free of your tax dollars support of communities, ran and helped organize the only distribution points available, coordinated with other charities, trucking companies (which is what I did on this end) to get supplies in and help stabilize things. They also did it faster than government response and resources could allow in a great many cases. Many of them are sticking around for as long as they are financially able to to continue providing support during the clean up phase. Or at least sticking around until that mission can be handed off to someone else.
People having downloaded zello provided a way to communicate where people had little else. It also led to a fair amount of duplicate calls for assistance because not everyone is on the same networks. Its still a great resource to have. The more options you give yourself ahead of a crisis the better.