Should I have to delete a transition to change the length of a clip?

No, you can drag the upper left or right edges of the transition to drag trim the in or out points of a clip. You might have to zoom into the timeline a bit before you can grab the upper portion of the transition. It's a great way to adjust transitions. You can choose the edge of a transition and add or subtract frames by number entry for a more accurate adjustment.

Even simpler - just select the clip you want to adjust so that it hightlights in yellow. Then double-click on the Timecode display
Then hit either the plus or minus key (to taste) and type in the exact number of seconds or frames you want to lengthen or shorten the clip. Hit Enter and the clip will conform to the new length. No need to target any edge or handle. That plus magnetism can make interior scene timing really, really easy.

FWIW.