It's obvious that AMD could have chosen to increase the size of the Renoir/Lucienne/Cezanne die by the few percent that would have been needed to add two or more extra CUs. That's not the question. The question is, was it worth the various trade-offs that they made in the final chip that was produced? I suggest that it was. At the time that it was released, it was the fastest game in town in it's full configuration. We also know that AMD has been capacity constrained with their APUs since Renoir was released, so the limited number of CUs has evidentially not harmed their ability to sell the chip. If we like it or not is not really on their mind.
Going forward, we know that, save for a refresh of Cezanne on N6, VEGA8 is done in APUs. There may be a cut-down version sold in the value sector, but that's about it. It did what it was supposed to do, and is serving well where it is used.
I look forward to the next generation of APUs.
I wonder if AMD will leave any ray tracing abilities in the RDNA2 CUs in APUs? I doubt that they will be sufficient for game use, but, they may have other uses.