I only really care when they've got a fairly hefty manga and cut it down to one arc, and that's it.
Code Breaker, which isn't my favourite fictional work by any stretch, isn't worth watching for only 13 episodes. The manga is over a hundred chapters and several story arcs, 13 episodes is barely an introduction essentially.
Or for a LN example, Legend of Legendary Heroes. All this world building, character development, and basic epic-ness was never going to fit into 24 episodes and the anime knew it but royally screwed over the invested viewer.
So, 13-24 episodes? Fine. Write original content to fit the time allotted or commit to the time needed to adapt your source material.