I’m not going to target individuals here, that’s not really in the community spirit. Just read through the comments, and think a bit out some of the things you yourself wrote as well.
That is just nonsense. Like with any field, you have to work to get into it. No-one “lets you in” to be a fireman, a doctor, a banker, or any other field either. You have to put in the work, look for opportunities, and be willing to make sacrifices to do any job, and especially field-based conservation work. It’s no more a red flag than not letting people off the street into an emergency room operating theater is a “red flag”.
Differing opinions are excellent to have, indeed that’s one of the primary drivers of advancement in the sciences and in other fields, but they have to be informed opinions, otherwise they’re worse then useless, they’re actively detrimental.
And yes, we can help as this recent publication indicates (and yes, as one of the people asked to contribute to this paper I have some issues with it and feel that it paints a bit too rosy of a picture, but it does show that the efforts we make can and do make a difference):
Unfortunately, conservation work is not the most effective way of dealing with the various problems we face. I used the examples of firefighters and doctors earlier intentionally as conservation workers are like EMTs and firefighters, rushing about trying to mitigate damage that has already happened.
What we need are not more people in conservation as a field, but people in politics, education, business, law, agriculture, restaurants, etc who have a conservation and ecological ethic to their behavior.
Think of it a bit like making seat-belt and helmet laws for cars and motorcycles, or building codes. Those pieces of legislation make it so that road accident fatalities drop and injuries are less severe, and make it harder for fires and injuries to happen in the home, making the job of EMTs and firefighters much easier.
Complaining that “no-one will let you in” is utterly ridiculous, you make the opportunity to take part, if not out in the trenches then where you can in your own field.