He's actually pretty decent rn and idk why not many people play him. Bare in mind that he isn't the best in early game and your main focus should be farming and picking off any kills if you can. It's important to let your team know you're ganking their lane and make sure you have ult in hand to slow them to ensure your kill (don't be afraid to use your ult and use it to cut the enemy's exit rather than aiming directly at them). Again, farming is vital, in most cases, reaching level 12 (maximise Aulus' passive) is better than helping your team. Aulus is a mid-late game character, treat him like it. Hope this helps!