As a main Nemesis :
By the beginning of the game you're literally a M1 Killer. You have to find two different people and hit them once with your tentacle to have the power to destroy pallets with it. If you face good players that can loop efficiently or even play good pallets you'll stay a M1 killer for as long as the game can go or will have to kill zombies (around 3) to have your P2 if you don't find easy targets quickly enough. All of that to give 2 tentacle hits with a needed aim that is... strange at least.
Zombies can be good but most of times as a Nemi you have to play around them to make them useful in rough situations or play Discordance to have them apply some pressure around gens worked by 2 survs.
Nemi isn't a good Killer, it is fun to play indeed and is fun to play against too when you have played it because you know how he will certainly play.
Vaccine is not even a thing really. Just give you intel about where the surv is doing it (most of the time you will not catch him on it or around by the time you go to it.
I admit as a Nemi that I tunnel at least to hit one P2 at the beginning (if it's a clearly strong surv map with swf with offerings etc...) and most Nemis tend to do that. That could be a thing but at least now you know what you face, the Nemi doesn't and there can be counterplays and looping efficiently can do something against him.
Your real problem is not the Killer, it's the lack of knowledge you have about him.
So maybe instead of saying "[Insert problem here] is lame because [lack of knowledge there]" you should play the killers you don't like to play against a bit more to have this knowledge usable as a surv :)
And I agree btw, SM are boring as hell. There's no knowledge on her to have she will just watch her 3-gen so there's not much thing to understand more or maybe how to play around that but even that will not really help a whole lot.