I am a small scale forester (hundreds to thousands of acres). Supposed to burn is ... complicated and not necessarily true. Many forests in the PNW have had indigenous Americans burn them regularly because it improves forest health. These fires were typically kept small and well maintained to avoid damage to the trees. White settlers put a stop to this practice, and natural fires were considerably less common than anthropogenic ones in some regions.

So it might be correct to say that fires can be healthy for forests, but "supposed to" is more difficult to assert.

I just finished limbing, brush clearing, and preparing burn piles from a section of my forest because removing fuel is good, but most forests in America are young planted forests. They have smaller trees, less diversity, higher than typical density, and small trees that can cause fires to climb to crowns (where they then become deleterious rather than helpful.)

If we were to return to indigenous practices of regular burning, we would likely see healthier forests. But I'm not sure we'd see as much timber production from them. Since that's what most forests are held for... I don't see practices moving away from trying to maximize timber while minimizing cost any time soon.