Short answer … don’t delete the sketches, just hide them in the Item list (which means they are always available later just in case you need them again). Often, they will be hidden automatically.
Pretty much everything else continues to work the same even if you ignore the history feature. In exchange for the slight change in how sketches are handled, we can now have multiple different unique sketches on the exact same plane if needed (automatically numbered to keep them separate, but you can rename them if desired to find them later more easily).
I sympathize with the pain of having to learn something new while under deadline pressure, but overall, I think Shapr3D has done a fantastic job of adding new functionality with minimal changes to older workflows.
Having said that, if you can eventually spare the time, I highly recommend learning enough to take advantage of the history feature. It will likely save you a lot more time in the future than you have to invest to learn how to use it.