I mean, that's technically Isekai in the sense that they're pulled in from another world but it doesn't embody even single one of the tropes associated with Isekai anime (I mean, I guess, bad animation but it wasn't badly animated for the period and region!).
If it was an Isekai anime, only Eric (sorry buddy, I'm about to throw you under a very big bus) would have gone through, the rest would all be "natives", and Eric would be even whinier, even more cowardly, way more of just a jerk, and both the girls would be absolutely ALL OVER Eric ALL THE TIME (one of them probably in tsundere way), for no apparent reason at all. Presto would also be female, scantily-clad, and also all over Eric all the time. and probably look about 12 but be technically 300 or something (UH OH). The Barbarian would still be a child (sorry I forget his name), but like, seriously age-inappropriate things would be happening with him and the anime (yeah even a modern one, if it was Isekai, because they tend to have the social attitudes of an anime 20 years older than them) would think it was hilarious. Ranger would be like, drastically dumber than Eric, and maybe have a rivalry but constantly be defeated by his own stupidity and Eric's innate superiority. Venger would be an even more thinly-veiled homophobic stereotype (but admittedly also probably more badass), and Dungeon Master would probably be perving on the girls.
I mean, hell,
Rise of the Shield Hero basically is the "What if only Eric came through?" anime in a lot of ways (because the lead is a cowardly whiner who only has a shield to fight with), and it's NOT good (despite being one of the least-awful Isekais).