Marines on the front lines in WWII were told not to worry, they had Navy bluejackets with rifles, there to back them up. That way the Marines fought harder and never retreated.
For the Navy anything that’s shoots something less than a 5” projectile is a challenge. Their forte is large crew served weapons not small arms.
Unfortunately, there is some truth to this. Way back in 1981, when I went through Marine boot camp at San Diego, the training we got with the 1911A1 was, IIRC, about an hour long class followed by firing two five round magazines while an instructor had his hand on your shoulder and his leg between yours so he could control you if you did something stupid. A recruit had recently offed himself on the range was the story.
Later, as a marksmanship instructor and a SNCO I got further training, but the reality even back then was that if you weren’t in a combat MOS you probably only qualified annually, and only with a pistol if it was your T/O weapon. This was years back in the Marines, where the philosophy was “every Marine a rifleman”. Pistols were not really seen as combat weapons, they were more of a personal defense or police item. I’d bet that’s even more true now than it was back then.
Recruiters come from different fields, and some probably don’t handle sidearms at all during their daily duties.
It seems like the Navy actually does more with recruits and the M9 nowadays than the USMC did back in the day, since a pistol is more likely to be part of a sailor’s work requirements. Obviously this sailor screwed up in spite of that.
I don’t think any of this is right, and there should be more training with sidearms in general, perhaps even only as part of prep for recruiting duty, but as others have pointed out, you can’t wave a wand and make it so overnight.