For example, recently released IK Multimedia T Racks Tape Machine collection. One instance of the plugin takes about 15% of one core. In a large project this is a lot and you need to think where to use it or use freezing. Then you have a suite of plugins by Acustica that use a variant of dynamic convolution (volterra kernels) to simulate equalizers, compressors or reverbs. Virtual synthesizers like Diva in pristine mode and enabled multi core can also take a lot of resources. You really need to budget what to use where so that it won't break up - which is a skill in itself, that hopefully in the future won't be relevant as much.