Steve, Your points are very valid and I think you see it the same way I do except for the part about the ticks. No doubt a tick is about half a second, but ticks do not fill orders. Liquidity has to be there to fill the order with liquidity providers offering in advance X amount of liquidity at current price, x amount at the next level, x amount at the next level and on down. So as soon as one level is gone it moves to the next and then the next as so on.
I think of it as 10 shelves of the same product in a store and when the top shelf is empty the price is higher on the next shelf down and each shelf downward raises the price again. So in order to get the product on shelf one you have to get to that shelf before the next person trying to get to it.
Speed matters in fast moving markets so if a strategy isn't dependent of getting product off of shelf one it is not a big concern. For a strategy that needs top shelf product it is a big concern.
I think of it like this. If I need to run to the store and get some of the product on shelf one, my chances of getting it are much better if the store is only a few blocks away rather than a several miles away. I hail the taxicab (wake up MT4), tell the driver where to go (latency) and run into the store and buy it (execution).
Execution can also be improved by dealing with brokers with redundant gateways (doors to get into the store), but that is a whole different topic.
Where there's odds . . . there's hope.