Assuming you're throwing Bandai in the mix as a 'high water' mark... the core problem is all three companies (Revell, Round 2 and Bandai) have completely different outlooks regarding their product.
Bandai has been working for the past 30-some years to make their product appealing to both the casual builder and the fanatic. It started way back when with 'System Injection', the ability to 'pre color' some parts by the use of colored plastic. The earliest was the use of 'one color' trees, white parts would be white plastic, red parts would be red plastic and so on. Then came the double whammy of not only putting multiple colors on ONE sprue tree (White, Red, even clear!) but actually molding some parts in multi-colored plastic! Mind, they don't do that specific technique anymore, or not so much, but the technology IS used in a weird but cool 'multi plastic type' molding, where they inject Polystyrene and ABS to create 'skeletons' of pre-assembled moving joints which one then attaches the various plastic bits to complete the model.
(Disclaimer, Bandai doesn't seem to make 'real' subjects as plastic kits anymore, totally concentrating on genre subjects. I'd like to see what Bandai could do with, say, a pre-colored snap fit 1/48 scale P-51D Mustang.)
And it all serves the ideal of giving the customer a pleasing finished product regardless of the skill level ability to 'finish' a kit.
Revell, it seems to my eyes, is stuck in the '70s. 'Real' subjects get the maximum treatment, making nice displays. Their search for quality goes to leasing molds from other companies (generally Italiari). But Genre kits, those are toys, not worthy of that same dedication or attention to detail. As long as it looks kind of like the subject that's good enough because who cares, it's not SERIOUS, it's only Star Wars. (and I'd still like to know the story behind the choices that led to that rather terrible TOS Enterprise.)
Round 2, they've got so much going on and such seemingly limited resources, coupled with the problems inherit with dealing with a Chinese 'turn-key' factory to actually realize the product.. honestly, I'm astonished they get ANYTHING done. But their core culture seems to believe that what they make are boutique, niche products (which IS true) so they're not really gonna worry, because they know that if they set their goals low they can always achieve them.
(my example: The 22" Eagle is pretty cool and it seems to have sold well. I argue that had they made the same kit but at 12" the smaller size and lower pricepoint they could have sold at least 10 times what they've done. Big kits with big prices limit sales, especially worldwide.)
Different companies, different corporate ideals and culture. They each believe that they have the right formula for corporate success.