You seem to hint that this is inherently a bad thing, as if through acquisition a product is somehow diminished. But is it?
Arguably Microsoft bought Github and it's better for end users. There's a usable free plan now with features being added on it.
Sure, some acquisitions are being made to kill off competition but Salesforce doesn't want Slack to kill it, but to develop it. Perhaps the original vision of the product won't survive, but let's not prejudge that.
Also, very few products are created where the creators envision it as smashing through tech giants. Most are created to be sold, so that profits can be used to create other products. It's less of a question of standing up against acquisition and more about making a product that's worth enough.
Creating a company where original innovators keep control and mange to grow it privately is a wet dream. To grow it fast enough in today's world, you need investors who want to have an official slice, to have a public company and a publicly traded company answers to shareholders who can decide whatever they want.