There is this belief in this war that a cellar or a basement is a fighting position, it is not. It’s typically a hole in the ground with ZERO fields of fire. Yet it continues that Ukrainians would rather sit in a basement instead of building defensive positions utilizing the basement as a strong point. This ultimately fails as the only way to defend it is to leave cover and expose yourself on open ground, typically resulting in injuries or death depending on the enemy assault force etc.
There’s also an issue of constant repairs. Trenches need repaired throughout combat. This is literally never done by most units though. There were countless times we would go out with the 59th to take over a position. We would bring supplies to reinforce trenches (sand bags, angle iron, etc) to build out bunkers, firing positions etc. we would get rotated out and another brigade would take over. 5 days later we go back and ZERO or negligible improvements were done. Usually the extra supplies we brought to build improvements sitting exactly where we left them and the Ukrainians sitting in holes smoking cigarettes vs digging.
Trench defense is pretty simple: You’re either sleeping, digging, or defending. If you’re not sleeping, you’re digging. If you’re not digging, you’re defending. If you’re doing neither of those you’re sleeping. The problem is this is rarely done. And not doing this erodes the ability to defend and hold a position. You could put 100 men in a trench, if it isn’t constantly improved upon the 100 men will achieve nothing. You put half that amount in the same trench and they actively improve the defenses, they will do 10 times better and likely survive with less injured.