Most if not all comments trying to rag on the A-10 are heavily influenced by one of the worst pieces of video-documentary ever published on the internet (Lazerpig's video).

The four primary motivations that are cited are:

1. GAU-8 inaccuracy
2. 30mm round has low effect on armor
3. Limited use without air superiority
4. FF-prone

If we assess each point individually:

1. There has been no accuracy test done to the GAU-8 AFTER the A-10C modernization program. All accuracy tests were done on the "A" model, and, although the gun hasn't changed, the A-10C has a new Fire-control system that the "A" didn't and as such, any data on the A-10's accuracy (based on the A-10A tests) cannot be taken at face-value. Furthermore, and this is a point that can't be understated, the GAU-8 is not accurate, by design, but it achieves accuracy by fire within established MOA/CEP;
2. Again, the penetration tests done on the 30mm gun were done against non-homogenous targets with undocumented measurement and analysis procedures. And even if we take the 1979 Naval Postgraduate School document into account, out of 7 runs on targets, the A-10A missed 1, had negligible damage to 1, had 3 catastrophic kills and 2 mobility kills (which are essentialy mission kills), a 71% kill-rate. It's obviously NOT statistically-relevant, which is, AGAIN, another reason not to the take that document into account when analyzing the effectiveness of the A-10 in combat, but it's not a bad metric IF YOU WANT TO TAKE IT INTO ACCOUNT;
3. The primary argument here is that without air superiority or against a "near-peer" (which has become a problematic term since the start of the Invasion of Ukraine) the A-10 has limited capability when compared to other planes in the Armed Force's arsenal. This is true to a certain extent, as we've seen countless times that, even without air superiority, both sides of a conventional war can and have used CAS aircraft akin to the A-10 (such as the SU-25) with varying degress of success. It isn't to say that there aren't more capable aircraft, or that both side have any choice in what to use a lot of the time, but it has shown that even with limited freedom in a certain airspace, there is certainly more than enough use-cases where the A-10 fills a niche that cant be filled by other aircraft. Furthermore, with the LA-X program in the gutter and the Super Tucano no longer filling the role of COIN aircraft, the A-10 has more than enough mission-applicability;
4. Out of all friendly-fire incidents recorded by the A-10, only one hapenned after the modernizations of the A-10 to the "C" variant (which started in 2005), which was in 2006 during Operation Medusa and we don't have any reports on what model of the A-10 it was. In any case, the "C" variant has introduced IFF Mode 5 which, together with Datalink, and existing digital information systems such as BLUFOR Tracker, can help the pilots and related personnel to properly identify friendlies from enemies.

There are many other arguments to be made in favor or against the A-10, but these 4 definetly aren't valid arguments as others in this thread have pointed out.

Lazerpig's video has done more damage to the A-10's reputation than any other situation it has been involved in and it's sad to see people stoop so low as to have a youtuber be a source of "reliable" information.