The rear derailleur is the more complex of the two — it has to manage chain tension, guide the chain across up to 13 sprockets, and do it all under load and at speed. Front derailleurs are increasingly disappearing: gravel and mountain bikes have moved almost entirely to 1x drivetrains (single chainring, wide-range cassette), and road is following. Electronic shifting from Shimano Di2 and SRAM AXS has transformed the experience — motor-driven shifts are faster, more precise, and unaffected by cable stretch or dirty conditions. Mechanical shifting still works beautifully when properly adjusted, but it needs periodic cable tension and limit screw adjustment. If your shifting feels rough, 90% of the time it is cable tension, not a broken derailleur.