I think this reasoning is silly; the gameplay loop is to keep improving ships/modules/upgraded modules/general skills. Why should a CMDR who's taken the time necessary to upgrade these attributes be the one punished by being forced to handicap themselves? The gameplay loop is to improve at this game, not go backwards. I've talked to too many pilots who think they should be able to watch netflix whilst farming CZ's in their Corvette's as a reasonable place to set the difficulty bar. Also, watched 7 out of 10 CMDR's flying shieldless in and out of Sothis/Ceos and the other 3 out of ten running minimal shields if they could be to even install them. The current diff level is set to cater to players who will not properly equip their ships for the minimum defensiveness. I can understand why Fdev would set the bar here from a commercial standpoint, but that still doesn't hold water with me personally.
I hear what you are saying but have a few points.
They can either handicap themselves by reducing their reliance on their mods or the AI can be made harder. The practical result is the same.
As for improving at the game, there's two ways you can look at that. Improving by getting the best equipment or improving by increasing your skill at flying your ship.
Regarding a gameplay loop, it seems to me that's down to individual playstyle choice rather than being something you must do.
Finally, flying shieldless is a legitimate tactic and can make the game more of a challenge. Winning in combat isn't the only way to 'win', sometimes escaping by the skin of your teeth can be just as rewarding.