That btw was one of the #GooglePlus features that really pissed me off and made me use it a lot less: the +1'ed by a friend promoted content, which more often than not was irrelevant to my interests, as it often included family photos of people I only followed for a specific interest. Along with the What's Hot posts, which increasingly became mostly about 'celebrity' nonsense, they just polluted my stream with noise.
The influx of mainstream users also made #GPlus go quickly downhill.

#GooglePlus features that were killed early on that I really missed:
†Followed By Stream, where you could see the posts of those who were following you. Handy way to connect with people with similar interests, and to mute those who followed you just to spam.
†Keyword/topic subscription, so you could follow posts based on interests, rather than people, without having to manually search. Much better than the promoted +1'ed content that later 'replaced' it.
#GPlus

As for #GooglePlus:

I was a GPlus user from the early beta period. While I was very active during the first couple of years, my interest in creating original content dwindled after Google removed interesting feature after feature, till I remained only as a lurker and occasional commenter.

Especially during the early adopter period, before Google's focus for #GPlus seemed to switch to mainstream users, it was an engaging platform. It was interest-oriented, rather than existing-contact-based.