I guess I don't analyze it quite so deeply. I've been making music and enjoying the new features. What do you mean by Sonar wants to be more modular?
I think Cakewalk took a bold step to introduce the purchase model they have chosen. I believe it benefits the end user far more than it does them. The monthly or yearly "non-subscription" plan holds them to a certain standard or expectation which I have to admire.
It's a commitment to roll out a new model every single month. Usually the improvements are substantial beyond mere functionality with plugs and the common bugs. These improvements have more than offset the cost of the software if purchased separately, moreover all additions are designed to work inside of Sonar.
Go price vocal alignment or drum replacement software. Go price the better plug-ins if they were sold separately and you can see the value start to add up. Look at purchasing some of the comparitive software instruments separately...it starts to add up. It's becoming less and less necessary to shop for any additional plugs or effects.
There are very specific directives involved beyond simply eliminating bugs as feature requests trickle in. The competition does this whenever, however, wherever and this would be the less stressful route to take for them.
This is real progress that bridges the gap between end user and software engineer which can only be a good thing.