You're confusing realism with presentism, or perfectionism (in the sense that the present is "perfect" and fully developed).
Realism is neither.
Optimism is the rejection of unwanted, unpleasent, or inconvenient truths.
What I find hard to understand is that you pit realism as the antonym of optimsim. The correct antonym is pessimism.
Both optimism and pessimism are biases. Realism is the absense of bias.
Realists are navigators, optimists are starters, pessimists are never-starters :)
You need bias to move things forward.
That's perseverence without denial.
Realism to correctly assess the situation and dynamics.
Hope and/or perseverence to follow those through to their potential.
Again: optimism denies reality. It gets you into trouble eventually, even if it can glide over some rough spots. At best, optimism can limit self-sabotage or inhibition. It does nothing to change the Universe itself.