After all the miners and the economic majority could decrease the blocksize under BU if they deem this to be necessary, BU just takes this power away from the development teams and returns it to where it belongs.
Return it? You are implying that it was like this before and that it was changed through time.
This is an example of how the other side manipulates with words (nothing was taken away, ergo nothing should be returned to "where it belongs").
I am indeed saying that, since not increasing the blocksize represents a change in the economic policy of Bitcoin, since the original vision of Satoshi clearly included an increased blocksize, and there is presently a divergence from this vision within Core. Even Jeff Garzik made this clear recently:
An Economic Change Event is a period of market chaos, where large changes to prices and sets of economic actors occurs over a short time period. A Fee Event is a notable Economic Change Event, where a realistic projection forsees higher fee/KB on average, pricing some economic actors (bitcoin projects and businesses) out of the system.
Failure to increase block size is not obviously-conservative, it is a conscious choice, electing for one economic state and set of actors and prices over another. Choosing Future Fee Market over Today's Fee Market. It is rational to reason that maintaining TFM is more conservative than enduring an Economic Change Event from TFM to FFM. It is rational to reason that maintaining similar prices and economic actors is less disruptive. Failure to increase block size will lead to a Fee Event sooner rather than later. Failure to plan ahead for a Fee Event will lead to greater market chaos and User pain.
The game theory bidding behavior is different for a mostly-empty resource versus a usually-full resource. Prices are different. Profitable business models are different. Users (the set of economic actors on the network) are different.
We only know for certain that blocks-mostly-not-full works. We do not know that changing to blocks-mostly-full works. Changing to a new economic system includes boatloads of risk.
The worst possible outcome is letting the ecosystem randomly drift into the first Fee Event without openly stating the new economic policy choices and consequences. The simple fact is *inaction* on this supply-limited resource, block size, will change bitcoin to a new economic shape and with different economic actors, selecting some and not others. It is better to kick the can and gather crucial field data, because next-step (FFM) is very much not fleshed out.