Pure Poison types: were they worthless before the boost?

Of course, Fairies are now a thing so it's not so bad. I'm aware that dual typed Poisons can fare very well too. And I've heard in gen1 it could hit Bug super effectively as well, but otherwise after that and all the way to gen5, Poison could really hit one type super effectively, and the said type already has tons of weaknesses. Were you underwhelmed by that? Or did you think it was still workable?

For me...it's a bit of a mixed bag. I've used some that actually ended up being welcome additions to the team, while also some that, while weren't bad, were also kind of underwhelming, and to the point where I just felt having to hit only one type that could be covered by most of my team members couldn't cut it, and to the point where I just felt it was the worst team member as a whole because of that. So personally, I'd rather something that has an actually decent movepool or stats to really end up being usable.
Just my opinion, though.

Before Fairy-Type was added, I never really thought twice about Poison-types but never really considered them worthless. It was more of a type that I didn't prefer using, I tend to use very standard base typings like Fire, Water, Grass, Dark, Ice etc dual-types over Steel, Ghost, Poison, and Bug types.

Also to be fair, from how I see it, Poison types didn't have a lot of exposure in the games or chances for the players to use a Poison type. There were only a very limited amount of pure-poison before Gen 6 and the generations before included one or two pure-poison types throughout the whole game, which is easily forgettable. Again, there's nothing wrong with Poison-types but they just didn't have the same amount of accessibility like Fire-type would have to players, making them seem "forgettable".

I haven't competitively battled since Gen IV and pure Poison-types didn't get much of a look in there so I'll ignore that.

Using them within a game I don't think Poison-types are useless - certainly unless I have a Psychic-type in my team in a Kanto or Johto-based game I've always found Muk and Koffing very tricky to deal with. Seviper is pretty nifty as well. Unlike Bug-types there aren't a lot of incredibly weak ones designed to fill up early routes either.

One thing I will say against pure Poison-types though - Trubbish and its evolution are two of my least favourite designs possible of all time.