Do you feel a let down when you always stayed Deluxe - then booked a moderate, POFQ, because of current prices and my lack of a corporate job
Now with the furlough - we have moved to POP next May 2021
Do you think we will still enjoy a week in WDW staying at Pop Century ?
I'll work backwards.
I have no idea if you will enjoy a week at POP.

I know I would enjoy a week at POP very much because I like POP.

However, years ago---okay, fine, decades ago---we're getting old

--- DH & I spent a "budget week" at All Star Music, and quite frankly, we didn't love the resort at that point. (That was when the All Stars shared buses ALL of the time, not like now when it's just during quiet times.) BUT, we still loved our week at Disney.

So basically, it comes down to how much of your overall trip enjoyment you attribute to your resort and in relation, how much time you p;an to spend at the resort. We spent almost no time at All Star Music beyond sleeping and getting ready for our day. I think we had one or two meals over the entire week in the food court.
For the first part, do I feel a let down if I have to down grade? Again, no. We would rather a budget trip to WDW than no trip to WDW, and we'd rather save money on the resort than to give up other things, if possible. Every point in our lives is a different situation. A trip with just DH & I was and will be different than trips with the kids. 20 years ago DH & I enjoyed our trips with relaxing sit down meals and lounge visits, but with our kids right now, it's breakfast in our room, counter service meals and pool supervision instead.

It's not a worse trip or trip not worth taking. It's just different. And a decade from now our trips will be very different again.

There's no reason your 2021 trip can't be a great one. Pick a few new things to try or places to check out and be positive.

I hope you have a great time!