Whilst we in the UK have been encouraged for the most part to see our cultural roots as unimportant, as we are all the same, anyone can be British, we can take the favourable bits of different cultures and use then to make our own more vibrant etc, that is not often the case in other parts of the world, even in Europe.
England as a country has been pretty well defined for over 1000 years. Great Britain as a singular entity for nearly 300 iirc. We haven't lost land, we haven't been conquered, or ruled by an outside force (from a purely English perspective), so we can't understand the emotions of what drives a conflict like this.
Consider the Scottish independence vote. 45% was it that said yes to leaving the union? And that's before the issue of Brexit came into the picture. Consider the troubles in Northern Ireland.
As another example, Hungary was chopped up in 1920, with lands Hungary had owned for hundreds of years given away to other nations, including half of what is now Romania, and indeed a section of Ukraine which is known as Karpatalja. These regions held many ethnic Hungarians who were suddenly separated from their countrymen, from their culture. In the areas where they are a majority, they still fly Hungarian flags, speak the Hungarian language primarily and refuse to be Slovak, Ukrainian, Serbian etc in any meaningful way, and the break up of greater Hungary is still felt keenly by many in modern day Hungary. That is after 100 years. 3 generations at least have never known greater Hungary, or have lived in "Hungary" yet the feeling is still so strong.
That's what is at the heart of this war, at least for the men and women on the ground. Bringing those they see as brothers and sisters back into the fold. Reclaiming land lost to them that had been historically theirs for centuries, united under the banner of one nation again.
I fully support Ukraine by the way. I've been many times and it breaks my heart to see it at war this way, I was just trying to paint a picture of the feelings of different peoples that for us in the UK can be hard to empathise with.