Those glitches with the social jigs also happen without mods. The mods just give you an easy way to get rid of them.
Also, for my playstyle, the game is unplayable in the vanilla state. That's not an exaggeration. It simply stopped working. Originally, I installed mods to be able to continue with my game instead of restarting over and over or moving from town to town all the time.
In principle, statements like the one in the quoted thread are just boilerplate language that allows for refusing any support in such cases, which in and itself is an understandable position for a company. It's important to understand though that the issue here is not the mods themselves, but the overload to the system one may cause, because the mods let you do this. Given that this "overload" is, most of the time, the goal of using the mod in the first place (for example, playing with several families at once), this is something to keep an eye out for everyone who plays this old game with its engine limitations.