Interesting, but I'm not convinced the examples support the argument. English uses 'is' to refer to a permanent characteristic or a temporary state, depending on context. Other languages have two separate words (e.g. Spanish with 'estar' & 'es'). If the context is unclear, or you want to introduce clarity, say 'John is being grumpy' - rather than 'John is grumpy' - if you want to convey that John's surly mood is temporary or uncharacteristic. Avoiding the word 'is' often just makes communication needlessly long-winded.

Wave theory vs Particle theory is another matter - both are models that have acknowledged drawbacks, neither 'is'.

I do agree with the meta-point that trained clarity of expression can induce clarity of thought & is therefore worthwhile.