The NRA was not enthused about Heller as they were not sure that it would have a positive outcome. There was real risk of a decision that would not support the 2nd Amend. Heller was a mixed bag because of the necessary compromises that Scalia made to Kennedy. In fact, those compromises have been used in lower court decisions to strongly support various state bans and restrictions. Folks say that they are misinterpreting Scalia's wisdom and he strongly opposed the later occurring state bans. However, they weren't taken up and his strong dissents are meaningless as they led to no actions and the state bans still stand and are supported now by many precedents. That is the fear that if another case gets to the Court, Roberts will support precedent and enshrine such bans as Constitutional.
The NRA-ILA, separate from the NRA (supposedly), does good work. However, the organization is now tainted by the top scandals and it's unwavering support of one party and an untrustworthy POTUS. Could Democratic support become a force again. There are developing pockets of gun support in minority groups that should be nurtured and overt babble about conservative principles not related to the RKBA and sometimes hateful rhetoric on social issues must be avoided. The latter aids in fund raising from a targeted and shrinking demographic, so it is short term gain and long term loss, IMHO.
Also, their messaging of why the RKBA is important is focused only on the demographic - it works for funding raising for the moment, but is a long term problem. Fighting the Socialist Wave is ridiculous as a primary goal. No one is taking to the streets with an AR to fight Medicare for All, the Green New Deal or Free College. Yes, Free College is the first step to the gulags? Won't sell outside of true believers.
When an organization gets into such a fight, one faction 'wins' and chortles about it. However, if that faction stays - it still degrades the organization.
The NRA used to be 'feared'. Such battles reduce their intimidation factor. It was clear in the HPA debacle, that they underestimated the GOP support for gun rights. The bump stock debacle was another instance where it should have been clear to POTUS that he did not have to leap into the fray (his personality flaws are not really a THR topic). The issue could have been turned over to the Congress for hearings and legislation rather than another executive precedent against gun rights (even if bump stocks are stupid). Democratic candidates are promising antigun executive actions, continuing in the vein of past ones (import bans) and the Donald's tantrum.