From my understanding, the break up of telecom was a condition of the government giving Chorus billions of dollars to build the fiber network. They weren't going to hand one ISP a multi billion dollar network, it wouldn't have been a fair playing field.
I think the breakup of chorus has been great. Lines were open before if my memory serves me right, but it does feel like there is proper competition in the ISP market which was previously dominated by Spark and Vodafone.
Spark buying out all my favourite ISPs is a bit rough, but I definitely think things would be worse without it. You can get fast internet for $60-$70 a month, which is really quite cheap considering how critical internet is to everyday life.