Nah, the best use for Membership Reward points is for booking international travel on a foreign airline! Some examples of good redemptions I've had with Amex points:
- Biz Emirates ticket on a third freedom route that had low fees
- Upgrading premium economy Alitalia tickets to biz (back in the day)
- Aeromexico redemptions when they have a sale

So basically, if for one of your international holidays United doesn't have direct flights, or the award price is ludicrous, you will have some options open.

I focus my travel on United and use a United credit card for most spending, but keep airline spending on the Amex Plat and then very occasionally use points for this sort of thing.