I would tend to agree. I think most platform plays will prove to be uncompetitive for one reason or another - UNLESS - they can do something ETH cannot - AND - they become cross-chain compatible with ETH. If they do that, then they don't actually HAVE to be decentralized, because they can sort of piggy back on ETH. As ETH continues to develop, however, you have to revisit some of these chains.

E.g., MATIC has done extraordinarily well because they followed this strategy. However, it isn't clear to me that ETH with fully integrated sharding does not obsolete MATIC.