The team did nothing of substance to improve the rotation before the season and its why we have Freddy who is very good but inconsistent and a bunch of guys who projected to be 5th starter types. Relying on Wade Miley who was unlikely to pitch more than 120 innings or so best case scenario and Jakob Junis who hasn't pitched 150 innings in 5 years was unwise to say the least.
Arnold had to have an idea that Burnes was going to be traded which was the right idea but he had no real plan to fill in the rotation adequately after Freddy. Relying on Miley, Junis, Ross who hasn't pitched in a few years and DL Hall who has been a reliever was poor planning.
Still with all this said I see no reason to pay a high price for a short term starter when the chances of this team beating two of Atlanta, Philadelphia, and LA is very low.