のが残念だ

it's a shame that

→ の
phrase Rare #29,259
it's a shame that Follows a clause to express regret or disappointment about the situation described. The polite form is のが残念です, while のが残念だ is informal.
JA: 今日あなたといっしょに行けないのが残念だ。
EN: It's a shame that I can't go with you today.

辛いしか会えないのが残念だ

It’s a shame we can only see each other when things are tough.

— 鏡 (1975)

今日あなたといっしょに行けないのが残念だ

It's a shame I can't go with you today.

君が来られないのが残念だ

It's a shame you can't come.

彼女がここにいないのが残念だ

It's a shame she's not here.