Many years ago, someone suggested I was a market timer at heart because I traded an equity investment for a fixed income investment. His rationale was that I made the decision based on the price hitting an all time high. We then had a discussion about re-balancing portfolios and how that should be considered market timing too.
Any investor is ultimately both an active and passive investor. At some point, you must make a decisions about the investments held. It is true that buy and hold works over the long term as the data supports. However, which start and end point you select can have wildly varying results.
Benjamin Graham's timeless writings suggest you need to evaluate an overall allocation regularly based on market conditions. He suggested having 25% to 75% of your investments in bonds and varying this based on market conditions. Yes, you should make incremental changes based on market conditions.