This is the 8424th most frequent Japanese word.
惜しむらくは
"惜しむらくは" means "it is regrettable that" or "the unfortunate thing is."
Here, 惜しむらくは expresses a sense of misfortune regarding the short duration of collaboration.
私たちは素晴らしいチームでしたが、惜しむらくは一緒に長く働けませんでした。
We were a great team, but unfortunately, we couldn't work together for long.
In this case, 惜しむらくは is used to highlight a regret concerning the lighting situation of the painting.
この絵は見事ですが、惜しむらくはライトの当たり具合が良くありません。
This painting is magnificent, but regrettably, the lighting is not good.
In this sentence, 惜しむらくは introduces a regret or a lament about the insufficiency of time.