As someone who has built a few hobby speaker cabinets, you absolutely CAN make durable and high quality objects for the home out of MDF. Or even particle board. So I think using taxes to try to discourage the use of certain materials in favor of others is misguided and only likely to lead to manufacturers doing different but worse underhanded cost cutting.
The problem is not the material per se but using inappropriate fastening methods for the type of material and/or a design that stresses the material in a modality where it is weak rather than where it is strong. An example of an inappropriate fastening method would be a screw into the edge of a laminated panel and the joint not glued.
For an example on the done-right side, if you look at any knockdown speaker cabinet kit from e.g. Parts Express, the MDF parts will have bracing and grooves where the user is meant to use wood glue, and screws mainly just to hold it together until the glue sets.
In furniture an example of using MDF in a way that almost has to be intentionally bad design: I have a tall chest of bedroom drawers where the drawer slides are suspended 2.5" off the internal walls by horizontal rectangular blocks of MDF. The blocks are oriented in a way that gravity and the torque on the block causes the layers of the MDF to de-laminate. (Picture riffle shuffling a deck of cards.) The resulting sag in turn makes the drawer slides no longer align.
Almost anything else could have been done to make this design better. They could have rotated the grain direction of the MDF blocks 90 degrees. They could have oriented the blocks vertically in the long direction. They could have used 2x3 lumber (vertical or horizontal) instead of MDF. They could have actually made the sides as thick as the facade pretends they are. (The sides are hollow.) They could have brought the sides in to where the drawer slides actually are. Etc. etc.
Some of those things would have cost more or made the (lying) appearance of the furniture less substantial looking. But some of these solutions use the same (MDF) material and same or similar amounts, just different orientation. Either the person who designed it was an absolute dumbass, or it was deliberately made in a way that would fail after more than 90 days but less than 2 years.
Mandating different materials doesn't protect against stupidity or malice.
Ok, I asked for cases where MDF isn't just a cheap shitty replacement and you gave me one.
But the efficacy of such a tax is based on the proportion of MDF that goes to crap, short-lifespan products. I don't have numbers here, but if there's a whole lot more crap furniture than hobby speaker cabinets, I would still be favor of policies discouraging the use of these materials.
The problem is not the material per se but using inappropriate fastening methods for the type of material and/or a design that stresses the material in a modality where it is weak rather than where it is strong. An example of an inappropriate fastening method would be a screw into the edge of a laminated panel and the joint not glued.
For an example on the done-right side, if you look at any knockdown speaker cabinet kit from e.g. Parts Express, the MDF parts will have bracing and grooves where the user is meant to use wood glue, and screws mainly just to hold it together until the glue sets.
https://www.parts-express.com/Knock-Down-MDF-4-ft-Subwoofer-...
In furniture an example of using MDF in a way that almost has to be intentionally bad design: I have a tall chest of bedroom drawers where the drawer slides are suspended 2.5" off the internal walls by horizontal rectangular blocks of MDF. The blocks are oriented in a way that gravity and the torque on the block causes the layers of the MDF to de-laminate. (Picture riffle shuffling a deck of cards.) The resulting sag in turn makes the drawer slides no longer align.
https://en.wikipedia.org/wiki/Shuffling#/media/File:Riffle_s...
Almost anything else could have been done to make this design better. They could have rotated the grain direction of the MDF blocks 90 degrees. They could have oriented the blocks vertically in the long direction. They could have used 2x3 lumber (vertical or horizontal) instead of MDF. They could have actually made the sides as thick as the facade pretends they are. (The sides are hollow.) They could have brought the sides in to where the drawer slides actually are. Etc. etc.
Some of those things would have cost more or made the (lying) appearance of the furniture less substantial looking. But some of these solutions use the same (MDF) material and same or similar amounts, just different orientation. Either the person who designed it was an absolute dumbass, or it was deliberately made in a way that would fail after more than 90 days but less than 2 years.
Mandating different materials doesn't protect against stupidity or malice.