The new icemaker will very likely have a different wiring connector going to it--a smaller one that will definitely not fit the replacement ice maker in that kit. Instead of making an adapter plug of some sort, they have you change out the whole dang wiring harness--it goes to several components and I believe it may even include a new thermistor. I'm sure there are reasons for all these changes--i just don't know what they are. Perhaps another member can chime in and shed some light on this for both of us.
Sounds like there are options that don't require all the extra work--i can't speak to their quality or expected longevity though. They may be good, they may not. I always just go with OEM parts by default, and I have for years now--I've had too many headaches or premature failures trying aftermarket/3rd party stuff, and I've given them up as much as possible. I always wondered why/how cheaper versions of these parts could be produced, and ultimately the proof is in the pudding. Some stuff will work fine, at least for a while. Other stuff will give you headaches from the moment you try to install it. I'm over trying to save money buying aftermarket unless they're the only choice left. I'm sure exceptions probably exist, but they're so few and far between that I prefer not to take the risk.
If you're only looking to get a couple years out of it, might not be a bad gamble while avoiding the extra work by going with the aftermarket one... I still wouldn't endorse or install them for my customers though.
