My employer does have a luxury of focus in its product offering, though we do have a moderately heterogeneous approach in development, certainly compared to many of the peers that operate at similar scale.
Heterogeneity in compute location has a multiplicative effect on accounting, security, capacity management, network management and is dilutive in terms of expertise -- instead of being able to justify the worlds leading experts in one system, you now need more staffing to cover a wider surface area (and they all need to have collaboration overhead to ensure they arent working at cross-purposes in strategy or tactic.)
I think this belief in marginal benefit from "right tool for the job" is a local-optimization where the costs of coordination and overhead are not borne locally and so are generally undervalued/discounted.
My employer runs on a single cloud provider, but -- do to its scale and closeness to core competency of our business -- we do operate our own CDN infrastructure, and this is a decision I happen to agree with. As a result of this division, I am acutely aware of the impact it can have on an engineering organization and only in certain specialized use-cases would advise considering DIY or multi-cloud.
I hear this sentiment repeated frequently, but I’ve never heard multicloud as leverage actually getting a better deal than an exclusivity deal. If you have a different experience I’d love to connect and learn more - email in my profile.
You can leverage the high quality network infrastructure from Google while using your own DC for Compute Heavy Load.
Use Azure for your Windows specific workloads.
Go with AliCloud in China.
You need to be big enough so that running it yourself is doable with a certain amount of quality. Which does imply many teams and workloads.