This is simply not true.
In the old system you could build every single building in every single province (well within some parameters).
In the new system without CS you cant do it. With CS you can THEORETICALLY do it, but not in practical sense.
Yes, with CS you can develop provinces, but no, you will not be able to develop many provinces to the level where you can build all buildings in each one. It simply costs too much, and if you go for it, you will fail.
Also lets not forget that now there are fewer but more powerful buildings in game. The fact that you cant build each one of them doesnt mean that the new system doesnt work, it just means that you need to change your strategy/the way you play the game. If you have fewer construction slots, use them more intelligently. Its not like the game is unplayable if youre unable to develop each province you own 45 times.
In the old system for 50 gold and 10 mp i could add +1 tax in any province that i wanted(not counting modifiers) Same goes for manpower, or trade power. The old system gave you a flat guarantee bonus no matter the territory.(again before modifiers)
in the new system, the buildings only are worth it in higher developed provinces imo. 40% tax increase from a temple is very different comparing a 2 dev tax base compared to 10. As they only add a % of what you already have. They do not add a flat #. in the lower ones, you are limited to one maybe 2 buildings slots, with not a lot choices because the dev is too low. The only way to make the buildings more worth while, on top of adding more options both in the building that is worth it or in the # of buildings that can be made is by changing development. In many ways people with poorer provinces were nerfed, just due to their land.(the terrain modifier has issues as well, but I wont get into that. )
I don't mind some parts of the world being more difficult, but this new system really punishes a lot of people. especially in the new world. I should also mention the costs of buildings has gone up, making them not only more difficult to make in mass unless you are swimming in cash, but it will take a long time for them to pay off. Again, even more so in some parts of the world, making them not very viable if at all. in the end, there are some areas where it is just not worth building at all, or you are so limited, you are left without a choice. That doesn't sound like something I would like in a strategy game. Sure, there may be some strategies to get around that, but again, you are now more or less forced into those. (by reading your post, i would believe you want some good/intelligent options as to what you can do. the system currently feels like it restricts it in a lot of areas. especially without the dlc)
I should point out i never really expected every building to be able to built in a province with this current patch.(though the best provinces in the world should be able to imo. just due to being so "big") but i expected my options to be good. and currently, in a lot of areas, there are not. especially without the dev system.
So no, I do not agree with buildings being better overall. In poorer provinces, you are limited to very few options, that wont be as good. Which in turn limits your options even more. I should also point out that there are a fair number of provinces within 3 development of being able to get another building slot. While it may be more towards an exception rather than the rule, that is still a lot of provinces.
I should also point out while the game is still playable, it just feels like you are playing a very sub optimal part of the game without the dev system. It is not so much that the system doesn't work as you are talking about, but more here is part of the system that by it self feels incomplete replacing one that worked, and here is the other half to the new system to make it full(requiring a dlc). Especially as i pointed out, the older system use to do the same things that the new one does.(but without a dlc) You can see my other post for that.