This is why for high-power switching they were quickly replaced by gas-filled tubes, long before WWII, e.g. with thyratrons (General Electric) and ignitrons (Westinghouse Electric).

Semiconductor devices have much lower conduction losses than even gas-filled tubes.

While conduction losses are much less a problem with semiconductor switches, many of the semiconductor switches have high switching losses, which limit their use to low switching frequencies.

Silicon carbide devices have lower switching losses than the older semiconductor devices, and gallium nitride have even lower switching losses than SiC devices, so both enable great increases in switching frequencies, which has many benefits.

As a bonus, in the future (when SiC crystals with a better quality will be available) silicon carbide devices will enable the production of high-voltage switches that require much fewer devices connected in series to reach working voltages of hundreds of kilovolt, or even of a few megavolt.

Nowadays, thermionic vacuum tubes or thyratrons remain sometime competitive in pulse switching applications, but only for very high voltages, i.e. above 50 kV. Even for such applications they have a too short lifetime, and there are better semiconductor alternatives, except that this market is too niche, so the big semiconductor device manufacturers do not bother to make such devices, which sometimes forces the use of obsolete vacuum tubes or thyratrons.

Only for the generation and amplification of electromagnetic waves in the microwave frequency range and at very high power, special vacuum tubes may remain preferable to semiconductor devices (e.g. the magnetrons of microwave ovens or the traveling-wave tubes still used in many satellites).