That tariffs are in use is not proof that it is untrue. Even with the current dumpster fire we still trade with the US, but that obviously does not mean there has been no harm.

For countries, tariffs is not something that is just shrugged off as it impacts their economy, there will always be political countermeasures to strongly discourage that tariffs are applied that harms them. Retaliatory tariffs, impact on other negotiations and relationships, etc.

For companies, tariffs harm profits and fair competition on both supply chain and consumer side, depending on where the tariffs are located. The company would strategize for maximum profit margins, circumventing tariffs, remove countries from their supply chain, and focusing on more profitable markets.

It wouldn't be a boycott the same way it is now of course. It would be a slower process. But tariffs is a way to force the market and always have wide negative effects. One just hopes that certain long-term side-effects (like high import cost causing focus on driving down local supply cost) is worth the impact (local cost of living increase, drop in investments, drop in friendly reputation).