It was an important ship to the shrinking Black Sea fleet. The secondary explosions went on for a long time so that ship was packed.
But you say a destroyed small town in the Donbas was of more importance. Hhmmmm, that is a difficult case to make.
1) Turkey has the Bosphorous closed to any warships (Russian, Ukrainian, or otherwise) since last year; only those returning to their home port in the Black Sea are allowed to transit.
2) What material could a landing ship carry that couldn't also be carried over land by the far more extensive (and more efficient) rail networks?
3) "But you say a destroyed small town in the Donbas was of more importance. Hhmmmm, that is a difficult case to make." It all depends on how much Ukrainian military resources were attrited as a result. After all, as seen with Bakhmut, Ukraine had no issue throwing absurd amounts of military personnel to fight the Russians over a "small town"; if it's down to a war of attrition, the raw numbers favor Russia. A landing ship that had been out of action for over 12 months isn't going to change the calculus on land.
(On a side note, do you have a source video regarding the secondaries? The videos and clips I've seen have shown only one secondary explosion of note.)
It was an important ship to the shrinking Black Sea fleet. The secondary explosions went on for a long time so that ship was packed.
Novocherkassk was a small ship, damaged and removed from duty at sea a year and a half ago, with no expectation of a return to sea before the end of the war. Get serious.
Maryinka was a fortress and the civilian population was militarily irrelevant.
The Russians destroyed the Ukrainian armed forces and their infrastructure from a distance. As long as the Ukranians don't mind getting destroyed, the Russians will destroy them. The Ukrainians fortified the position because it had strategic significance. They fought to the death for two years because it had strategic significance. They lacked the means to stop or withstand the Russian artillery. They lost a strategic fortress because they cannot perform miracles.
Maryinka holds much more significance than a small, unusable ship.