Protectionism is expending resources to direct production to areas where you have weaker comparative advantage — it is, in other words consuming value to force your people to create less value.
There may be very specific cases where very carefully tailored uses of it are good for certain long-term interests or risk mitigation, but mostly it is waste — and extremely subject to corruption from those invested in inefficient industries.
> consuming value to force your people to create less value
That's the "spherical cow on a frictionless plane in a vacuum" of economics.
Protectionism is probably a good idea when the competitor is temporarily subsidizing various industries to build a permanent comparative advantage that can then be abused, either by being an effective monopoly, or by shaping your enemies to be logistically unprepared for war.
Protectionism does almost nothing to prevent that comparative advantage from being built unless all other consuming countries in the market also add a tariff. And most of them will not. Using the WTO to coordinate a response is a much more fruitful way in such a situation (but the WTO has been neutered by Trump).
There may be very specific cases where very carefully tailored uses of it are good for certain long-term interests or risk mitigation, but mostly it is waste — and extremely subject to corruption from those invested in inefficient industries.