The UK also has a FPTF voting system, yet the Lib Dems won enough votes in the past to form a coalition, and currently the 5th biggest party in parliament (Reform) is leading the polls, and the 8th biggest (Greens) is often-times polling in 2nd place. Even if you might not win the next election, you can help build something that gets the "only-ever-vote-for-1-of-the-2-leading-horses" people to also vote for it after that.

Some people will never vote for parties that cross ethical lines like genocide, omnicidal climate change, capitalism, oligarchy... For these people the lesser-evil is still way too evil.

“It is infinitely better to vote for freedom and fail than to vote for slavery and succeed.” - Eugene V. Debs, Appeal to Reason, 1900-10-13.

“Wage-labor is but a name; wage-slavery is the fact.” - Eugene V. Debs, The Socialist Party and the Working Class 1904-09-01