I'm a fan of having several tiers/divisions for Tests and ODIs, especially as a means of getting more nations playing. I wouldn't even mind if stats were separated as Tier 1 ODI/Test, Tier 2 ODI/Test, etc. If quality of cricket is the main obstacle towards having all teams play each other an even number of times and/or getting more teams playing, then let's bring in Tiers and have some form of quality control.
But the reality is that none of the decision makers care about quality of cricket. They care about revenue and politics. The Big 3 decide who they want to play in their bilateral series based on potential income and and various political considerations. They only signed on to the concept of the WTC on the basis that this status quo is maintained. Therefore we end up with this weird schedule and points system.
Having Tiers/Divisions would force the Big 3 to play whoever is in their group, and they won't have that. If they would accept that, they would accept a proper WTC where everyone plays each other Home and Away within a certain timeframe.
Also worth considering that most nations, as mentioned in this thread, struggle to cover the costs of Test cricket atm. If NZ had to play each of the 11 teams home and away for the WTC, or if they were in a Tier that did not have India/Eng/Aus in it, they'd probably go bankrupt. So I suspect it is not only the Big 3 who would object to a different system.