> Virtually all previous particle discoveries were predicted

That's not true at all. To give just few examples.

Electron was not predicted but Thomson found it during first fundamental particle discovered came from cathode‐ray experiments, not from a prior microscopic theory of matte. Remember this was during thr 19th century.

Another one is the muon discovered in 1936 which was detected as "heavy electron" in cosmic rays. it did not fit any clear theoretical need in nuclear physics at the time, leading Rabi to quip “Who ordered that?”

Heck there are many more examples that I will bypass the comment limits if I tried to list them (resonances in particular will be very numerous).

You can of course move the goal target by narrowing what you mean by particle but this is exactly why physicists try to define what they talk about before making an argument.

> There is no such motivation here. There is no theoretical or significant practical benefit for the FCC, it's basically a jobs program.

Really? There is a huge volume of the feasibility study about the physics program of FCC. Are you claiming that it is false. Have you even read it?