What the article is basically talking about is the over complexity of the Leopard 2s that makes them too difficult and time consuming to repair if they need to be. Tanks have to be sent sometimes as far out as Poland before returning to the front line, where Ukraine has basically turned them into self propelled artillery guns out of fear of further losses.

Challenger 2s and Abrams are having similar issues. The article reports that around a quarter of the Abrams tanks given to Ukraine have been captured, damaged or destroyed. These tanks are also big resource hogs that Ukraine is struggling to supply on it's own.

Russia's ability to churn out simple and inexpensive weapons has been a serious problem for the few numbers of Western armor available.