I'm not at all an expert in hardware, but I have experience using chiplet-based chips in production and optimizing for them. Those chips are better from a performance per $ point of view, but they don't necessarily achieve the highest absolute performance. The main limiting factor appears to be latency for communication between chiplets. If you write anything with shared mutable memory you are affected by this. Simple atomic operations like compare-exchange is much slower if the threads run on different chiplets.

However I fully expect this to be the future. The performance per $ is what really matters to the bean counters, and us software engineers will just have to write better software to work around it, perhaps with something like NUMA-aware scheduling that understands chiplets.