Being third in the market is independent from the quality of services IMO. Whether the services are being offered that a lot of businesses need is a different question. The services Google Cloud does offer tend to be well designed but many of them are simply not what established businesses (and their engineering organizations) are accustomed to. Lower marketshare is not a direct consequence of engineering excellence (or an alleged lack thereof).

Conversely, simply having more market share doesn't mean AWS services are well engineered and the engineers are smarter (they might be, but you cannot make this claim).