What those two said. If you don’t stock anything on previous age goods and are relying solely on trading current age for previous stock then you’ll have a much harder time keeping up.
If you look at the technology tree you’ll need current age and 3 ages below. But you’ll need the previous ages in higher quantities than you’ll need your current age stock. However you’ll find it far easier to get your current age goods while in that age then if you wait until later to obtain those goods because most of your rewards will be current age
And yes trading is a option, but the marketplace isn’t necessarily as active now as it once was due to event buildings being much more productive then they used to be in goods production.