Take a player who has never done PVP before and put them in the meta FDL, and put them up against someone with significant PVP experience in an unengineered build of choice - the skilled player will win.
Before Engineering existed my CMDR was once pulled over (while in his FDL) by a wing of CMDR bounty hunters, who had negligible PvP experience, consisting of an FDL and two Vultures. The result was that I shot down both Vultures twice and the FDL once, then forced the FDL to flee before being destroyed a second time, and left with a mostly intact ship.
If any one of that wing had had the FDL that's sitting in my CMDR's storage now, I'd likely have lost against just that pilot. They were PvE pilots who had never really engaged in PvP before and didn't know the first thing about fighting other CMDRs, but I'm pretty sure they had all their controls bound and could muddle through the tutorials...which is proficient enough to close a huge gap with a sufficiently superior vessel. I'd have to be landing shots ten times as often to win, which is only going to happen against a very new player trying use plasma against me.
My point was that the engineering is a barrier to entry but the practice is a bigger barrier to entry - just having an engineered ship won't mean you can actually do it. It's just an entry ticket to get started on the git gud grind.
Learning combat is an enjoyable part of the experience of becoming a better combatant. Even for those that view combat as a means to an end--which is a position that's increasingly hard to justify--skill progression is quite organic.
Having to do things one would never otherwise do, or repeat them far more than one would otherwise find enjoyable...that is a barrier. That's why Engineering is problematic.
The majority of my CMDR's friends list haven't logged on in years because when 2.1 showed up and dropped this massive barrier between them and the main activities they had already been enjoying for thousands of hours, they left for greener pastures. If it were a simple matter adapting to new tactics, or new ships, and learning new skills, like we'd all done a hundred times before, that would have been
fun. Radical overhauls of fundamental mechanisms, incredible power inflation, which transformed combat into something almost unrecognizable, all cordoned off behind collecting thousands of units of inexplicable garbage and jumping through Engineer unlock hoops---not so much.
Take a player who just bought the game and give them a T9 with a docking computer and engineered thrusters and FSD, put him up against a guy with 1000 hours of trading in a stock cobra mk3. The new player will make far more cr/h. Same with exploration, or mining, or (non-AX) PvE combat. In all of these activities it's equipment that is the progression path much more than skill.
A rather spurious correlation. The master in the Cobra struggles to keep up not because of a lack of Engineering, but because of the order of magnitude greater cargo capacity of a T9; which is something anyone who's been playing for a thousand hours could readily afford. If you're a trader who is learning trading skills, you're going to make the money required to outfit a better trading ship simply by trading, which is the kind of organic progression that everyone had before Engineering. You won't get the Engineered defenses or increased jump range that way, but piloting, cargo capacity, and learning routes are significantly more important.
Same goes for exploration; the equipment matters even less here. I can do almost anything with just a million credits, because that's more than enough to put an FSD, fuel scoop, SRV bay, and scanners on a Hauler. Won't have the same jump range, but 99.95+% of the galaxy will be within reach and I have more than enough experience to make the hazards of exploration trivial, no mater the ship.
Combat benefits more from Engineering than anything else, by far. This isn't to say that skill isn't important--obviously it is--but Engineering is also mandatory for much combat content and Engineering doesn't really occur organically, except at a glacial pace, unless one has very diverse interests. I probably had less trouble with it than most, but it was still a lot of senseless repetition to reach the specific goals I was aiming for.