You say that, and they said it (only 90s kids will remember "fifteen days to slow the spread") but as of right now, it's a truism. Maybe the lockdown worked to ease the stress on the medical system. Maybe only the first 15 days of lockdown did that, or 30. I highly doubt that the entire year of lockdowns saved the medical system, and I would be willing to bet the effectiveness of the lockdowns in preventing a collapse of the medical system ended within the first 3 months. So suppose that's true, 3/4ths of the lockdown and all the mental health and depression related deaths associated with it were unnecessary. I don't know when the lockdowns stopped being effective in protecting the medical system, but I know it wasn't this morning.
Some amount of those deaths are attributed to lockdowns that were unnecessary.
Also, you can't quantify the hypothetical death toll in that scenario in any real numbers, to say "would have skyrocketed" is unfounded. I could understand "would've been higher" that sounds reasonable.