In my case, the bulk of my actually active followers went to a diaspora pod (pluspora.com).

In my case, the bulk of my actually active followers went to a diaspora pod (pluspora.com). Only a few hundred out of thousands, but the level of engagement is about the same.

The reason there's no automated way to transfer contacts is because Google+ is a closed system. Back in the day, before G+ even existed, there were attempts to make integrated social media clients that interoperated between Twitter and Facebook etc. But then, Twitter and Facebook decided to ban any such usage. This is what led to the "Federation" of open source alternatives such as diaspora, Mastodon, etc to form their own social media ecosystem entirely separate from the closed system big boys.

I mean, they wanted to give you the interoperability you're hoping for. But the closed garden social media services actively did everything they could to prevent it. Google is no exception in this regard.

If you want to never have to go through this again, I'd suggest looking at the various Federation/Fediverse options - they offer the ability to migrate from pod to pod if you want, and you can even switch from one service to another and still keep your same followees (you'll need to get your followers to switch the address they're pointed to, but they won't need to change services at least).

The biggest ones in terms of user base are diaspora and Mastodon. They're the ones which offer the least smooth ability to migrate from one pod to another, though, and currently they don't directly Federate with each other.

Friendica federates with all of the Federation/Fediverse, and it offers the ability to smoothly migrate from one pod to another via an export/import process.

Hubzilla also federates with all of the Federation/Fediverse, but it's a younger project that's a bit rougher around the edges. It offers the unique ability to have live "clones" across pods so you don't even have to do an export/import process to migrate. In fact, the "clones" automatically kick in as necessary if one pod goes down or gets disconnected from the internet. If you're comfortable with installing the server software, you can even spin up your own personal Hubzilla pod just for yourself so you can have a local "clone". That way, you'll always have a local copy of all your stuff. You could even use it to post/comment/like/etc when your Internet connection goes down. After the internet is connected again, all of your updates will get whooshed out to your other clones (and the federated services of your followers/followees).

If you, like me, don't ever want to go through the prospect of having to export all your posts/Collections/Communities/etc and then ... ehh... doing something with it... well, I'd suggest taking a serious look at Hubzilla's capabilities.

Reference: The History of Hubzilla:

http://www.talkplus.org/blog/2016/the-history-of-hubzilla/
http://www.talkplus.org/blog/2016/the-history-of-hubzilla/