Open enrollment for 500 EE — how do you actually pull it off without a benefits admin platform?

We're doing OE on spreadsheets + carrier portals + paper enrollment for stragglers. 500 EE. It works but the admin team puts in ~120 hours over a 6-week window and we still find errors in January.

For people who've moved off this model: what platform did you land on, what did it actually solve, and what didn't it solve (decision support? dependent verification? life events mid-year)? Cost reality-check welcome.