I wouldn't say that at all.
Obviously none of them are masterpieces. They're basically glorified advertisements, let's be honest, but clearly the original trilogy had a lot of heart put into them.
Most notable is the soundtrack for each film, which I would consider very close to masterpieces themselves. By far they are the one thing that everyone should know these movies for.
The animation itself isn't bad, aside from maybe one or two instances per movie (something to be expected from a relatively low-budget, direct-to-DVD movie). What people really take issue with is the art style and character design which comes down to personal taste (in my own taste, I love it).
The stories of each one, while fairly basic, aren't particularly contrived either, certainly not a bad story by any means. Overall, the original trilogy carries as its through-line the idea of coming into your own, of finding who you're meant to be, which is a fantastic message to begin with. Alongside that, how many modern movie franchises can you think of that maintain a narrative and thematic through-line like that? I wouldn't wager many.
If you look at the production behind these movies, the effort that went into them, and just the pure heart and soul they evoke, I find it really hard to say they are completely awful, or that they deserve to be forgotten. Objectively, I wouldn't rate them as anything below mediocre, which is a lot coming from an age where most movies with ten times the budget are comparatively worse where it counts.
And at the end of the day, movies are art. Art is subjective. Don't let the objective quality of something ruin its subjective meaning to you. The Bionicle movies will always have a place in my heart from what they gave me as a kid, and even now as a wiser and more experienced young adult there are things I can still appreciate in all of them.
Yes, even The Legend Reborn.