I'm not all that hardcore on "Classic", I want to relive the old zones and the old world and it seems like most people I'm taking to is feeling the same. We would prefer to have quality of life improvements regardless of them actually being in the game at in 1.12.2 or not. Like the "Automatic Quest Tracking" to actually track it properly without you having to actually trigger progress in the quest for it to show up would make perfect sense. It's no real need to make such a thing behave nonsensical just because it's "authentic".
Where to get materials and reagents you may ask? Buy for cheap off farmers in bulk or track Auction House lots. Get in touch with most big sellers. Communication is important here, send a whisper or write them a letter. It would be good for both of you to establish business relationships. Constant suppliers and buyers is convenient for both parties to save the time and effort.