I don't find that performance runs at % chance scale. When things perform poorly, they are often very consistent. With this architecture you can rapidly iterate & scale your poor performing core services, while the non-core services can run slowly w/o causing a big deal.
The usual alternative is redeploying and scaling the entire app to iterate on performance, which is a much slower process. If performance is a concern, microservices should be a big win.
All APIs have performance SLAs that are not consistent. You may have 50% of requests finish in 200ms or less, 90% finish in 300ms or less, and 99% finish in 600ms or less. You can do work to narrow the performance variation but performance is a % chance.
The usual alternative is redeploying and scaling the entire app to iterate on performance, which is a much slower process. If performance is a concern, microservices should be a big win.