the best tube amps are being made now.
modern power tubes are in some important ways “better”, i.e. kt-120, Kt-150 and Kt-170 have greater plate dissipation. So amps using those tubes can be designed which exceed past efforts, in a more compact form factor.
modern biasing controls have advanced, yielding better sound see, e.g., VAC.
even transformers have advanced; amps can be designed are quieter toroids with wider bandwidth. Capacitors and other parts are improved.
I loved my Mesa Baron, but 12 power tubes was too much to deal with. Keeping an old tube amp going is like having an old sports car - more ongoing maintenance is required than a modern design. To send it back to the factory cost over $500, round trip.
the build quality of my Rogers integrated is Nasa-satellite level, way better than anything from ”back in the day”