"particle physicists should focus on developing new technologies that could bring colliders back in a reasonable price range and hold off digging more tunnels."

Creating just a bigger version of the current collider with incremental advancements in technology is very likely a poor use of science euros. The money should be used to investigate other methods for particle acceleration and investigation. Some linear accelerator concepts could be much less expensive than very large circular colliders, but I imagine research into those areas are not funded due to the particle physics budget being mostly consumed by CERN.

This type of problem has happened in fusion research. The fundamental physics of how to build an economic fusion reactor still needs to be worked out, but almost all funding has been cut in fusion research to pour concrete and build magnets for the ITER project. It is clear that the $14 billion and rising reactor cannot lead to economically viable fusion reactors on any kind of reasonable timescale. ITER is currently planned to be fully operational in 2035 and, if the past is anything like the future, there will continue to be more delays.