The president/King argument is somewhat specious. Growing up in the 50’s, that was the justification for wearing a hat. That all changed when John F Kennedy went hatless at his 1961 inauguration and, overnight, hats went out of style. The same is happening with jackets, albeit a lot slower.
If you take it literally it might be. If you understand that a jacket and hat are more respectful/respectable and the reason it has gone out of style is not because the style of respectable clothing has changed, but rather because it has become the norm to dress less respectably, you will realize that it is proper wear a hat and especially a jacket for davening.