When I started at my current employer we were running our retail management software on DOS terminals connected to a SCO Unix box. My experience with the system was that it wasn't intuitive or easy to learn, but was pretty bulletproof for the veteran users who had been working with it for ~30 years. I learned as much of it as I needed to know, and got to the point where I could do some tasks without even thinking about which keys I was pressing.

I helped set up the replacement system and received a lot of complaints from those same users - some resistance to change, but also some legitimate failings of the new software. Tradeoffs in the network structure made it run more slowly at satellite locations, Windows 10 on all of the terminals caused network issues until we got updates and bandwidth moderation dialed in, and some employees needed additional practice using a mouse.

I see trade-offs between the old and the new here. The new software is easier to train new users (less arcane) and able to securely handle things like chip credit cards (which had previously needed a separate card terminal system) and charge accounts. At the same time, the old system was faster (for the limited features it provided) and was able to run more smoothly on older equipment (very little OS overhead, text only network transmissions).