Unfortunately the grim mechanics of FPTP makes that the case. Smaller parties need way more votes to win a seat. LDs are best placed, but I think many lefties will waste their vote on the Greens, because they still can't forgive the LibDema for the Tory Coalition betrayal.
A wasted vote is one where a party hasn't earned your vote. ReFUK is a protest vote and now seen as a threat to the mainstream. Why can't this be the case for Greens and/or LDs? Labour has no right to political hegemony, just ask the Tories.
In an ideal system yes. But we're in the very dangerous situation now where actual fascists are taking power. We are living in the final days of the Weimar Republic, and we must not allow the fascists to gain more power.
That's a global phenomenon, no doubt promoted by Russia in a sustained economic downturn. The system won't change until we vote differently. The overhyped ReFUK with a grand total of 4 MPs and falling have a vote share about the same as UKIP. Only Starmer wants to copy them. Consequences.