Working incrementally definitely makes sense. Also if you don't see a chance to do it in an incremental way you should probably take a step back and ask yoursel

Working incrementally definitely makes sense. Also if you don't see a chance to do it in an incremental way you should probably take a step back and ask yourself if the old application is maybe too huge and monolithic and check if there's a possibility to make it more modular. So you could split one huge application in smaller parts/services which can easier evolve seperately from the rest.