Electric shock with isolated material in the circuit
It boils down to current distribution, but let's start from the beginning.

In both cases you form a circuit with several elements in series. Some of them have excellent conductivity, like copper wires. You are of meager conductivity, but your shoes and ceramic tiles have even worse conductivity, they are dielectrics. As the dielectrics have contact to or are in between conducting elements in a geometric relationship they form capacitors. This circuit consisting of capacitors and resistors permit AC current to flow. Aside from some other effects the current should be the same order of magnitude in both configurations.

What's the difference now between both cases? When touching the copper wire you form a conductive connection with a very small area for the carriers to pass. As two conductors connect, there can't be a strong electric field either. Due to the small area the current density maximises and you can sense it. n.b.: you can't sense it at your feet, can you?

The other case differs as you touch a dielectric. This dielectric differs from the surrounding air but not very much to change the electric field dramatically. Hence the electric field vectors connect to your skin perpendicular and with merely unchanged field strength. At your skin the electrical surface charge influenced by the field causes a current, but this time distributed over the surface of your hand. You can't sense it.