There are ways to accommodate both a system that rewards repeat cruisers and makes them feel some sense of value and loyalty from the company (even if that is just a marketing ploy) and giving concierge guest an upgraded, elevated, luxury experience. If we look at other companies like Royal and NCL we can see some great examples of this. Concierge doesn't have to mean (and shouldn't be) just paying for "Platinum-level" perks, and top tier loyalty should not be the same as paying more.
On Royal & NCL, Suite/Concierge guests get upgraded bedding, espresso machines in-room, priority boarding & departure, a concierge lounge with food/drinks, VIP seating at shows, special party/happy hour events, dedicated concierge-only sun/pool areas, and dedicated suite-only upscale restaurants.
People with Loyalty Status get access to a lounge (usually a different one than concierge guests), welcome beverages, special party/happy hour events, discounted fares on certain sailings, free drinks, discounts on wifi, free photos, discounts on laundry, etc.
Yes there is some overlap, but nobody would ever confuse the Platinum perks on a royal ship for the same level of service as a Concierge, and concierge benefits rarely step on the toes of the the high-tier loyalty guests. As a platinum on Royal, I have never been shut out of a dining venue, or been unable to book a cabana at their private island...they have so much more capacity that they mitigate those issues. Disney has no such capacity.
I think if Disney had added a new Concierge-only restaurant to the Wish, a lot of the issues with getting shut out of Palo would have been eliminated. But just giving them priority booking for upscale dining when there is such small capacity for that causes issues.
I also don't see an issue with concierge guests earning loyalty faster. Other lines give double the points for suites, but they also have 7 levels of loyalty with top-tiers requiring 700+ nights...that's still 350+ nights in suites, which is A LOT of sailing!
DCL can most certainly follow a similar path, add new levels, increase perks, reward concierge in points calculations, add more dedicated amenities for platinum and concierge guests...but will they? Not now, no need to do so. Maybe/hopefully one day they grow large enough to do so.