I have just performed a test where I loaded 113,000 bricks (+ some emitters that were present on the default builds that made the total) on both my GTX 970 and the Intel HD 4600 which is integrated into my i5-4690k. Both tests were done at the maximum possible settings without use of any mods at 1920x1080 and the only difference between the two tests is the GPU that is being used. From a viewpoint where I was able to fit roughly 60% of the loaded bricks on screen at once here are the results:
GTX 970 (please right-click>view image to see the FPS);

Intel HD 4600 (please right-click>view image to see the FPS);

Though this test may not be the most scientific I think that it is reasonable to deduce that Blockland is no-longer as CPU intensive (speaking in relative terms) as it once was, though having at least a modern CPU will definitely make a difference that is not something that is unique to Blockland; if you're running a game like this on an old CPU you're going to get bad FPS, it would be the same in Gmod or any other game, really. It is quite plain to see that having a good GPU makes one hell of a difference no matter how you look at it.
You can all draw your own conclusions but I for one would quite pleased if you people would stop spouting this nonsense about Blockland being CPU-intensive; perhaps it was such 5+ years ago but nowadays, so long as you have a CPU that's even somewhat recent, the thing that actually matters is definitely the GPU.