You hate Phish, so you never got into "Jam bands?" I like Phish and the Dead, so I never got into the idea of "jam bands."
Phish and The Dead are very different bands. Likewise, Phish and other "jam bands" are very different from each other, as well. I never see people say that they never listened to Talking Heads, because they didn't like DEVO. These are individual groups and entities. I just don't get why they are always associated with each other or there's a need to mention one in association with why someone does or doesn't like the other. It would actually make more sense if I heard someone say they didn't like the Dead, so they never got into Phish, than the reverse.
Some people do like jam bands, just like some people focus all their attention on any supposed genre, because they can't really think outside the parameters, but it' ridiculous to me. To me, it's like believing that you have to like Silver Chair, because you listen to Nirvana. Nirvana wasn't a "grunge" band, they were a band that had some success and laid a blueprint that a lot of people tried to imitate, while their actual peers in the scene were all lumped together, but had very different sounds from one another. The Dead are The Dead. They aren't a "jam band," but they are THE jam band. Phish is their own thing, but were definitely influenced by the Dead and the idea of jamming out tracks in a similar way. From there, you're going to get a lot of people forming groups and deciding to lead with a lot of superficial shit, before the music. They are "jam bands" before they are bands at all. That's not every one, but there is a TON of those.
The Dead formed into what they formed into organically. Phish had years to morph into what they did, before anyone was really paying attention. These days, there are a ton of kids that believe they need to have 2 sets of music and fans willing to follow them, right out the gate, when they don't really have the material, experience, or skill sets to pull that shit off at all in any respectable way. I can't really entertain most of it at all.
But, if you're going to "get into" the Dead, then it would help to throw preconceptions and associations out the window, or you're entering into it with an unnecessary obstacle. My wife and I were even discussing it recently how funny it is that she "hated" the Dead, when I met her. She can't even tell me or remember what she thought they sounded like, before she realized what they actually do sound like. I tricked her with Shady Grove. She didn't know what she was listening to, so she liked it. It's better to just listen to it.
Also, Phish is great. Y'all are haters. "I knew a guy who I hated that loved pizza. I just can't eat the stuff." Just like the Grateful Dead, Phish has a lot of different sounds and eras. Try a slice without pepperoni. I don't like the shit with pineapple on it myself, so I just don't eat it. As for Phish versus the Dead, you're talking NY thin crust versus deep dish. Not everyone likes both. I do.