2 things:

When google plus was first implemented into youtube, it was a forced link. the reason it exists in the system it does now is because even the "1 million + " subscriber club of hooligans was complaining about it, making videos complaining about it, etc. It was a PR nightmare for what was already an unpopular move for an unpopular social media service.

What google wants is to make every google account work for every possible service. So far as I am aware they do not want to force you to link all your currently existing google accounts under one name, and aren't forcing you to.

In theory this is correct, and for most situations is. As I said before, I don't suspect malice, it's just a business move. moving everyone wholesale into a new system is much easier than encouraging people to switch a la carte.

The problem came when you had accounts on several separate google services using the same email. They all became bundled together, because "same account, same person." There were ways you could force a continued separation (which became a little easier to do as they saw how unpopular their decision was), but there was little information for the average user on how to do it - most of it in tiny light grey print at the bottom of the white page. No one was "forcing you" in a literal sense, moving your hands for you, but they were putting the burden of work onto the people who desired (or as I showed before, might need) the separation, the "status quo." therein lies the problem.

Youtube in particular is guilty of changing its interface in ways that its users hate, but makes youtube more ad revenue ( which is admittedly much less than it could be because of how google decides to run), rather than actually fixing any of the issues the users actually complain about (the subscription box has been junk for years now - to the point that some of my favourite youtubers use an email list to notify people of new videos instead). It's always easier to crop this change on everyone - think "New and Improved" pizza sauce on your average frozen pizza, which a few months later becomes "Original Sauce is Back!" when the original ingredients are more cost-effective.