Do you generally have a ton of events each day, or is it only one or two? I think there used to be a limitation to the number of events (not days) that would be synced to the phone, but that might not be the case any more. When I just checked Google Calendar on my 3 XL, the calendar I use for my hospital group's scheduling goes back at least as far as 2017 (I didn't bother scrolling further), and each day has 4-6 events, so that would suggest to me that there's no longer a limitation.
Go to Settings>Accounts, select your Google account, and look at the Calendar sync information. Does it say Sync Error? What if you turn off the sync toggle for Calendar, and then turn it on again?