How could it not be worth it??!!

Obviously it depends on the price, but Gold is the sweet spot on UA - Group 1 boarding, E+ at time of booking, *G lounge access, free checked bags (for those who care), etc. If I am not flying UA I will usually pay for a seat upgrade to E+, so Gold saves me a significant amount, esp. on family trips.

In the old days I would easily spend $500 on a mileage run, heck I spent $500 for Plat which is much less of a bump up.

If you are mostly flying with OPM then it seems like a no-brainer to spend anything <$1k to be comfortable for the next year. Especially if the alternative will be to spend a dozens flights in E-. And even worse if you travel internationally in economy.

If you fly mostly on your own dime then maybe you are better off as a free agent, unless you are a hub captive.