Are you saying large Transformers 1 mva, 10 mva, 100 mva, 500 mva are obsolete and should be replaced by switched mode power supplies? What mva is the threshold?
Eventually it will be worth switching out old transformers - they contain a massive amount of valuable copper and quite valuable steel, and their lower efficiency means every year they remain in service they are wasting $$$'s of electricity.
Transformers in cities can often be replaced with much smaller switched mode units underground, allowing the building housing the old transformer to be rebuilt as luxury flats to make the project much more profitable too!
I don't doubt switch mode could be smaller and cheaper up to some size, but I am struggling to see transformers larger than about 5 mva being replaced with power electronics.
Solar farms etc have inverters in modules I believe 500 kva each - and of course the power electronics are necessary there, there is no substitute.
I have a 20 MVA transformer that is nearly at end of life and would be open to cheaper replacements.
We already see these at the substations at each end of a HVDC link, China is operating well over a dozen of them with capacities of up to 12 GW (https://en.wikipedia.org/wiki/Ultra-high-voltage_electricity...).
Additionally, the price of copper is already at an/near the all-time high and it's not going to get cheaper, and the land on which huge transformers sit is shooting up in value... so in the end, market forces may push towards solid-state technology anyway.