I can agree with the OP in that Marriott doesn't offer up MVCI suites in quite the same manner as they used to in the past, but that mostly has to do with new properties with lots of unpurchased inventory.

So first, lets make sure we all do understand that Marriott itself doesn't really control MVCI unit inventory, the owners (people who purchased week ownerships) do. Once a property is essentially sold out, the only time Marriott can offer award inventory is when owners trade in their weeks for points. If the owner tries to rent that week (either themselves or even through Marriott), that unit will show up for paid rentals (cash as that is what the owner is expecting to get in return for renting their week out), but it won't show up for awards as there is no "cash" the owner would get. This has always been the case.

Now one problem with this is MVCI hasn't really changed the amount of points owners get for turning their rooms over to Marriott in years and years. But every year those points are devalued by various degrees. The effect is that over time, fewer and fewer owners (especially at properties that have higher annual maintenance fees and cost more to purchase into) are willing to trade their units in for points. They lose money when they do that.

With all that said, there are still many properties where one can still find award availability. It may take a little more patience and it will very likely not be found during higher travel periods for that location though.

For example, I stayed just last year (May) at the Aruba Ocean Club for a week in a 2 bedroom unit. And earlier last year when I was looking at options, both MVCI properties in Aruba had 2 bedroom award availability. The St. Kitts MVCI not only had availability but that included some 3 bedroom unites as well. We ended up not choosing St. Kitts as we have been there before but had never been to Aruba.

So there is award inventory that does show up, but you have to be a bit more patient than in the past.

As to the Plat line experience, I do agree that they definitely don't provide the same level of service they used to. Back in the day, they would call a hotel directly for me for various reasons (like staying at an RI and trying to get a 2-bedroom suite upgrade). They would call, talk with the hotel management and let me know if the hotel was willing. The Plat line doesn't seem to want to do those types of things any more. And in the distant past, I very rarely would have to wait to get an agent, but now, waiting seems to be the norm and actually getting an agent instantly is the aberration. So I definitely agree there has been a decline in service there.