What would happen if leap years didn’t exist?
Well, let’s say in tens to hundreds of years we will be very far back on the calendar. Winter solstice would shift 182 days which means it goes from December 21, to June 21 in 2777. Now this may seem unimportant to you since you are going to live till like 2030-2100, but for the following generations they will have lost the track of time and everything is going to be jumbled up. A lot of celebrations and seasons will start way later and we wouldn’t even know how far off we really are.
A lot of estimates made by then will appear earlier because multiple days were lost due to no leap year. Hence why leap years are important, so we can stay with time accurately and precisely.