Bitterness in a beer comes from adding hops during the boil. Traditional IPAs were made like this, and for awhile, you saw brewers pushing the IPA boundary by loading the boil with more and more hops. Boiling the hops extracted the alpha acids which create the bitter sensation. Dogfish Head 120 Minute is a good example of this.
About 10-12 years ago, starting with breweries in the Northeast like Tree House (hence the term New England IPA), brewers started to make light bodied beers that had very few hops added in the boil, but they would dry-hop (add hops during secondary fermentation and after the boil) the **** out of these beers so when consumed fresh they had a very strong odor and flavor of hops, but didn't have the bitter feeling on your palate. Part of Toppling Goliath's rise to fame was by being one of the first breweries west of the Mississippi to embrace this style and produce an excellent version of it.
If you first tried an IPA like Bell's Two Hearted, or even Confluence's DSM IPA and didn't like it, and have never touched them since, I'd encourage trying a hazy. They don't taste like the same thing.