It's difficult to imagine innovation of any kind not being rooted in the past. I draw parallels to the area of linguistics when any particular sentence has a theme and rheme - old information (something known) with new information (something unknown). Thus, there is a relationship between what we know and what we learn and it presents itself in the way we think and communicate. We even have a word, scaffolding, to refer to a teaching technique that helps learners connect what they know with what they are learning.
But the question about "creativity" always building on the past is interesting because of the subjectivity of the term. What's creative for one person may not be creative for someone else. If something is deemed "creative", then there is an inherent relationship that exists between the past and present, more specifically something that is known with something new.
Protections provided by copyright should end much sooner than stated by current law - starting with the removal of the Sonny Bono Act of 1998. Works should enter the public domain much sooner so that knowledge becomes more equitable. It's the old I v. we argument. I would rather see a reduction in copyright terms (70 to 50 years) than changes to the exceptions/limitations to copyright, although I admit that one hardly influences the other. Theoretically doing away with the 70 years worth of protection would not negate the necessity of needing current limitations and exceptions to copyright. These limitations and exceptions provide an immediate need (accessibility to knowledge) that is so important to who we are as human beings: knowledge intertwined with building relationships.
Example: Imagine a world where all published work would remain under current copyright protections for a period of five years, at which time would automatically shift to a Creative Commons license as decided upon by the creator(s): commercial v. non-commercial, derivative v. non-derivative, share alike, and public domain options. If we compare this scenario to reality, I believe that society (the group) would benefit much more than the degree the individual (or creator) would be disadvantaged. Just the sheer amount of exposure a creator would achieve in this scenario might put some at even a greater advantage than today's reality. Increasing the "long tail" (power laws) affords a greater distribution of power to those typically marginalized by those at the "head" (Pareto principle).
If we keep extending the timeframe for copyright protection (beyond 70 years), works never enter the public domain. Fewer works that enter the public domain or are licensed as Creative Commons stifle knowledge/relationship building and thus quell societal development. In contrast, making more works available through public domain/Creative Commons levels the playing field so that everyone has a greater likelihood to succeed.