The 2015 move was actually because the FCC had been repeatedly challenged by bolder and bolder ISPs over its rules, and the courts ultimately stated that the FCC didn't have the authority to stop ISP shenanigans and enforce its Neutrality rules under Title I in 2014, hence the reclassification under Title II.
So yes, the internet was quickly getting worse prior to 2015, and it was not a "steady state" as it had started from much more stringent regulations (than the 2015 regime) back in 2005, things had progressively gotten worse over a decade before coming to a head.