Sure. The general idea is that the density of the components has increased. SSI may have used photolithography whereas the higher density of transistors are using x-ray lithography. At one point there were issues about gamma rays from the ceramic encapsulent which had a greater effect when the circuit density increased. The materials had to be better. The clean room better.
Now what has happened in general, is a migration to BGA packages where the leads are non-existant, so even a 16 pin BGA will require a multilayer board to lay out. Muti-layer is greater than 4. It may need 8 layers or more. I've seen references to 40 layer boards.
Learn to program an FPGA, and you can design circuits of every complexity - simple gates, multiplexers, even processors.
Of course, if you only want to design digital circuits that consist of a few simple gates, there are easier ways, but these will limit your options when you want to advance to more complex circuits.