For enthusiast it's doable - you can simply side load those apps, things like graffene os (afaik) let you even install entire Google services and run it in sand

For enthusiast it's doable - you can simply side load those apps, things like graffene os (afaik) let you even install entire Google services and run it in sandbox to prevent it from spying on you. But if You want to hit the mass market, you can't rely on this 'tricks', and there is no easy way to make the process streamlined for average user. That's why the only big phone manufactured who isn't using google services anymore is Huawei, and it wasn't by choice. (I guess amazon tried it as well but only kinda)