To give you an example of an actual timing, in a recent SFO-MAD-LCG trip I landed at 14.13 and I was at the T4 lounge at 14.44. This included taxiing, deplaning, passport control (though as an EU national using the electronic gates), transit, COVID check and security. It helped that we landed on the closest runway at 14.13, so the doors opened at the gate at 14.18 (I have all these times because I was having a WhatsApp conversation with someone who was waiting for me at LCG).

In this example it was 26 min from arrival at the gate to the T4 lounge, so it would have taken me ~30 min to get to a GRX gate, which is a little farther way, as LupineChemist said.