Why do you think that? Lets just look at SDD with it's ride capacity of ~2000pph. This means in a 12 hour day 24,000 people can ride this ride. Assuming 50% LL capacity, there are 12,000 SDD LL available each day. In 2019 (the last "normal" year) ~11.5 million people visited Hollywood studios or an average of ~31,500 people a day. If "50% at best" buy Genie plus on an average day 15,750 people will have it.
Not difficult to see how the 15,750 people could take all 12,000 SDD LL for the day. Remember this is an average day, assuming 50% ride capacity to LL.