Then you want to fight FPTP and vote pruning by constituency, to make your vote matter.
You could vote blank, or a poop emoji to show your disconformity, but organizing or supporting a protest to reform the voting system might be more effective.
If we counted all those who don’t vote because it “doesn’t change anything”, those who vote blank or null, and those who vote knowing their vote will still get thrown away… it could actually make a majority.