Should I sell my Oppo 205?

Good at many, master of none.

They are beautiful players with excellent quality of build, so if you play discs, by all means keep it. I sold my BDP-95 and ended up later buying a BDP-103 for the ability to rip SACDs, which one can also do with certain Sony models, but after having two of those break, I went back to Oppo!

With the money gained from the sale, your unlikely to be able to replace it with anything that does anything it does much better, and it won't be able to do the other things .
If this was sold with a different label through boutique stores at double or more the price it still would have garnered great reviews and no one would complain about the current prices.
There's a reason they can still fetch the prices they do, even if they cost much more used than new.
Everyone is entitled to their subjective opinion. Here's and objective one.: 

Review and Measurements of Oppo UDP-205 UHD Player | Audio Science Review (ASR) Forum

While a bit dated, it's still pretty competitive, especially when one considers all else it does.

There is no reason to sell it and you can use it for other formats as well what i have discovered over the years is that when you sell something you usually always regret getting rid of a good or great piece of gear.