People are not running 'us' down - they are running the government down. They are rightly doing it because the sanctions package put forward by the UK government was initially pathetic, and is still way less than others, and gives his oligarch backers weeks or months to evade the effects. They are also doing it because the response to the Ukranian refugee crisis is equally pathetic as well as inept. This is all presented with the usual cocktail of lies, bluster and bullshit from Johnson, Patel etc.
Zelensky is a smart politician. He will say what he thinks is most effective to get the response he wants from his allies in this war. Of course he praised the UK in his address to parliament. It doesn't mean he is impressed by UK sanctions, material support to Ukraine or what passes for 'our' (by which I mean the government) refugee relief effort.
Why are you so keen to give Johnson and his government a free pass in the face of overwhelming evidence of their corruption, lies and ineptitude?