Should my company ditch testers and use Quality Coaches instead?

TL;DR: Quality coaching is a model you grow into, not adopt. That's because testing is an acquired skill, and teams must learn how to test. Pairing is an optimal way to learn about testing. As teams learn about risks, test design, and exploratory testing, they can preempt risk and build quality into their design. As a team matures in its quality practices, a tester may feel their role becomes redundant. This is a great time to introduce a quality coach.

A fairytale in tech

A long time ago (10 Julian calendar years, centuries in Bezo years), a fairy godmother was asked to devise a way of scaling testing in a hypergrowth company. The independent test team was small then, with minimal automation coverage. The engineering department was hiring rapidly, and as the number of product teams grew, so did the number of features being deployed. Consequently, this test team struggled to test quickly, rapidly becoming a bottleneck.