The problem is not that LibreOffice Calc is not an adequate replacement for MS Excel, it's that MS Excel is not an adequate solution for most of the things that people try to use it for. If you try to tell people to replace a bad tool with a similar tool that is subtly different, they will have a bad experience. 90% of the bad experience comes from using a VisiCalc clone, the remaining 10% comes from using one that has a subtly different UI.

Once you get over the learning curve, Jupyter notebooks are often a much better tool (and they have a lot of poor UI annoyances). A tool that provides the same flow and a simpler onboarding experience would be much easier to switch people away from MS Office, by not copying the bad things that Excel does, but by showing them that they can get away from all of the suffering Excel causes.

EDIT: A minor clarification: A better onboarding experience isn't just 'Jupyter but easier to install', it's eliminating the friction of having to lean Python to use a nice DSL that's embedded in Python. The end result would likely be closer to Lotus Improv or Quantrix Modeller than to Jupyter, but could be built on something like Polars.