To me, "sloppiness" is not holding to a basic level of quality. Being plagued by issues that also plague many other games isn't sloppiness, it's par for the course.
Oblivion's development wasn't rushed. The game was even delayed, as it was intended to be an early launch title for the XBox360 but got pushed back by several months. The thing with it is, Bethesda does not focus solely on graphics. As good as Oblivion looked, it wasn't a graphical powerhouse, Skyrim also had its graphical shortcomings, and even Morrowind didn't look as good as its contemporaries. For Oblivion in particular, they instead had a large focus on AI. They put a lot of work into AI, and not all of it panned out, likely leading to the delays as they had to rework things for the simpler system the game ended up with (and is likely why it feels rushed; similar to Skyrim which had a lot of work put into the Radiant Story system, that was gutted in the final game leaving it feeling rushed and incomplete).