Grid-scale power electronics are also extremely niche and expensive, perhaps moreso than transformers. HVDC is used where it has a significant advantage, but ease of conversion is not one of those.

> so transformers with their huge requirements for copper and steel are no longer necessary.

smelting some copper and steel and wounding it up is far, far, far, far cheaper than replacing it with power silicon(which might be smaller, but overall needs tons more of energy to produce)

It will be also less reliable. Transformers deal with any overload far better and routinely run for like 50+ years