We (two mature adults) plan to visit Vienna in 2022 if it is possible to go. It will be for 4 to 5 nights.

Twenty years ago we stayed at the "Hotel Konig von Ungarn", a great location at the top of Karntner Strasse. This time we wish to stay at the southern end of Karntner Strasse near the Ring road for a change. I have looked online reviews/pictures of several hotels, but still have not found anything.
My requirements are:
1) Well-kept hotel with pleasant and bright rooms, no dark red or dark green carpet/curtains.
2) No strange or creepy wall arts hanging in the room.
3) short walk to a Tram or U-bahn station.

Budget is very flexible. Thank you in advance.

I'm sorry I don't know if this is in the area you want, but we loved the Hotel Kaiserin Elisabeth
https://www.kaiserinelisabeth.at/en/

Does a "flexible" budget extend to the spendy level...?

Several years ago, we stayed at the Hotel Sacher not far from the Opera House and Albertina Museum. LOVED this hotel, but it was (and likely remains) very expensive. If the Sacher's rates take your breath away, look at the Bristol Hotel nearby. It's a Marriott and has view rooms overlooking the Opera House.

This is also near the Opera House: https://www.operasuites.at/

I stayed at the K + K Palais Hotel Vienna ... all means of transport are close to the hotel

Reading54 - I've only been to Vienna once and we happened to choose the Hotel Austria which we really liked. Very traditional but comfy, quiet, and very close to the Ring and bus/tram stops.

https://www.hotelaustria-wien.at/en/

Some years ago we stayed at the Römischer Kaiser, which we were quite pleased with. It's in your desired neighborhood, I think, just a couple of blocks from the opera and the Sacher (avoid the famous torte).

https://gshotels.de/roemischerkaiser/

Thanks folks, for your continued input.