Right but that's the point: the parent post is talking about those things as though they've obviously and clearly obsoleted the ITER design. Except that can't be true, because no reactor based on those technologies exists now, or is likely to complete construction in the near future.
So ITER is the correct bet: take boring technologies and build a functional fusion device with them that gets Q > 1. Because there's a fairly obvious corollary, which is that if you can somehow build better magnets, then the next reactor - DEMO, and actual power plants - can obviously be redesigned to take advantage of those magnets - they will not fundamentally change the internal dynamics of a tokamak, since it's the magnetic field shapes which matter, not the physical generators.
Everyone working with REBCO has always talked about "rapid breakthroughs" in about 5 years, and then 5 years later the story is always the same: it's considerably harder to build with these things then you'd think, they're still working through the engineering etc. It's not that it can't work, but it's not magically faster in the way people keep claiming and nor does it get you any closer to the actual goal, which is to get a Q > 1 fusion device functioning - which will, at all times, fundamentally require a very large vacuum chamber to do so unless magnetic field intensities are being vastly increased (and they're not: low-temperature superconductors can achieve far higher field intensities then high-temperature ones which is why the LHC and other particle accelerators use them[1] - some YBCO tapes might be able to do it, but manufacturing suitable quantities, of suitable quality, in long enough reels, and then winding magnets with them is an unsolved problem).
>Everyone working with REBCO has always talked about "rapid breakthroughs" in about 5 years, and then 5 years later the story is always the same: it's considerably harder to build with these things then you'd think, they're still working through the engineering etc.
Please cite the earliest REBCO-based fusion reactor promise date that has lapsed. I don't think reality agrees with your perception.
Importantly you can draw a straight line from REBCO-based fund raising and the amount of REBCO needed to be purchased for them. If "the engineering wasn't there" then that amount of money could not have purchased that amount of tape.
Also, how could ITER be the right bet when it costs so much and takes so long to build that it could never scale to anything more than a multi-generational science experiment (e.g. not a power source)?
ITER is a considerably more complex research device, designed and developed to generate and study burning plasma. It is also the first device of it's kind intended to do this. It is an entirely uncontroversial issue that the first version of literally anything is comparatively expensive compared to the costs of subsequent ones.
This is a problem the US Navy is intimately familiar with when it comes to shipbuilding as it is currently experiencing with it's next generation aircraft carrier design.
It is incredible though to see people saying that the ITER design is "obsolete" when the actual proposed replacement technologies have ongoing papers trying to move towards practical deployment as recently literally this year.
EDIT: It is worth nothing that I could be wrong in the end if the SPARC project succeeds[1], but there's a pretty heavy asterisk on that since ITER is amongst other things, a research project - the plasma physics modelling, supporting fusion research, even manufacturing and magnet winding research and other miscellaneous construction processes are all public knowledge which is shared amongst participating nations. It's been the only game in town for decades, and no one was wrong to try and build a fusion reactor 3 decades ago when it was as desperately needed then as it is even more so now.
That was the last poster child for "REBCO tape will quickly solve all the problems".
Oh right - incepted in 2010, cancelled in 2021. 11 years - over a decade - and no reactor in sight.