Yes, there's always been a way to set multiple alerts in Calendar but I'm sorry to say this is not the point. Alerts could previously be snoozed by simply long-pressing the Snooze button, regardless of the event reminder setting in Calendar. You could set a reminder at 30 min; the alert would you up and you could click Snooze and choose a duration to delay the next alert
I just ran a test with an event set to 5 min, 10 min and 15 min alerts and the Snooze button still doesn't let me choose a duration to snooze.
Your solution would be good for people willing to spend the time to set multiple alters on every single Calendar event they enter, but I'd venture that this is not practical for most of us.
To give you a use case: I typically set all-day events to have alerts at 9:00 AM. I have several of them for every day. The Snooze button allowed me to see at 9:00 AM which those events were, choose to work on the most important/urgent ones (depending on the new day priorities) and snooze the other ones so that I could tackle them later in the day.