I'll presume you played them to come to this opinion(otherwise it's grossly misinformed). They were never panned by critics, and actually were given fairly decent reviews.
The CD-i Zelda games, when released, were generally decent games. People just love to hate it on without having any knowledge about them besides that Nintendo hates them(and for absolutely no legitimately good reason. Like I said before, they're being immature brats about the games in every way. It makes sense to keep them away from the canon, but that's the only thing that the CD-i games blatantly have, they weren't canon. They had more than good enough gameplay quality, the graphics were fine, the cutscenes were funny and had tons of emotion, and their reviews were overall decent and somewhat positive). In fact, the magazine critics gave them good reviews. Better games just came out later(like OOT), that's all.
I could go on, but eh.