The problem with the "get gud" argument is that it inevitably is made by people that thinks twitch-based game play is the only thing to consider.
I feel experience and piloting ability are the main avenues of progress, but I certainly don't think twitch-based gameplay is the only thing to consider. Even when talking about PvP encounters I can't count the number of times my CMDR has defeated technically superior, or more numerous, opponents in more powerful, vessels through the use of superior tactics.
For example, I'm recall of forcing CMDR Old Sauveur's Python to retreat from my CMDR's FDL in a 1v1 way back in 1.4. The Python was the superior 1v1 vessel (though it's performance in/against a wing was always lacking) and Old Sauveur was the better pilot at the time. Still, I knew he had a very hot running loadout (PAs and beam lasers), so I kited him into close proximity of a star before submitting to his interdiction and fought defensively until I saw him start to overheat. I immediately went on the offensive, forcing him to burn a SCB charge. He responded by retracting his hardpoints, giving the 'o7', jumping out with crispy subs.
I've also shot myself in the foot, snatching defeat from the jaws of victory, while trying stuff that was as ineffective as it was unconventional, almost as often...but that's how we learn.
There's a lot of whining about carebears in ships that are near indestructible by most NPCs. But what they have done is used patience as a skill to overcome an inability, or a lack of will, to engage with opponents as dance partners. Which I think is fine: If I want to have a fun rush of a fight I take out my Eagle Mk II for Res site shenanigans; if I want to sit back with a beer and watch the fireworks I bring the Corvette. If I want something in-between, I bring my Mamba for general fun times or my T-10 for AX fun times.
NPCs are barely ever obstacles. None of the remotely threatening ones are anything but purely opt-in encounters.
If I'm looking for a challenge, as a player, from NPC content, I'm forced to have my CMDR do things that are profoundly immersion defying. Getting in an AX Sidewinder and trying to kill an interceptor, or taking an unEngineered Eagle into a High CZ, certainly make for a difficult time...but it doesn't feel right. Habitually self-handicapping doesn't make for a very organic or plausible experience, and it further cheapens material progress.