Terminator is a pretty bad example to use since after the second one, it too makes very little sense. T3, T4, and SCC all tried to milk the brand even though it was essentially done after T2 and really didn't need continuation. Every producer who came along had to really twist things to keep it going, and the result was always less than stellar.
Aside from that, I liked the line in T3 where Arnold says that "Judgment Day is inevitable." Maybe terminators that look like Arnold, or John sending back Kyle shouldn't be inevitable, but the message was that the fate of humanity would always lead to that. It was inevitable that their hubris leads them to building a super computer that was capable of wiping them out. If it wasn't Dyson, then it would just be somebody else. If it wasn't in 1997, it would just get pushed back to later. It's almost like inventing electricity. It was likely inevitable as long as people didn't wipe themselves out first.
But interpersonal events? Yeah, it's silly when those stay the same. It's ridiculous to say that someone like Kyle Reese, who originally states that he was born after the war can be exactly the same person born before the war. That is when things become far too stretched.
Having TNG characters would certainly stretch it that much. The original cast showing up on the Enterprise isn't as bad as that, but the way everything lined up still strained probability.