In my trade we use uninsulated butt connectors for splicing along with good quality shrink tubing that has the sticky sealant which is activated while heating the tubing. No issues of corrosion or bad connection, even many of our OEM replacement sensors and switches have uninsulated butt connectors and shrink for warranty approved repairs. Using an uninsulated type crimper one just has to be careful not to crimp too hard as you can cut the wire strands in the connector. This type of connector is used even in 460vac 3phase compressor wiring. I agree about butt connections looking amateur, but that's only the insulated ones.....especially when crimped with pliers...LOL, we've all seen that under the hood of old cars. I've seen many soldered connections in harnesses attract corrosion even if shrink tubed....possibly wrong type solder used.