I stopped OOO at 2 so I can't comment on 3, but I find the Candroids galling on several conceptual levels.
1) It is completely insipid that they are literally something we watch the hero buy in the series, I don't give a damn about its stupid coin theme. Bandai is not known for marketing things subtly, but showing the hero buying Candroids in hopes that children will mimic that is just crass and distasteful. We do see Shotaro use the Memory Gadgets in W to make them look cool but that's far less obnoxious.
2) The engineering of the transformation offends me. Long, slim objects are very easy to make transform into something else, it's why we got an assload of Super Robots based on trains in the 90s. The Candroids are the same type of lazy, despicable engineering.
The Memory Gadgets didn't all transform and the ones that did transformed into different sorts of shapes. They all had specialized functions that were so clear they called for very little exposition. I dunno WTF the difference between the Hawk and Octopus Candroids really is, beyond shape. They both seem to fly.
3) The way the Candroids can show up en masse for cheap CG spectacle is offensive. It indicates their disposable nature in-series and out-of-series is clearly meant to try and goad children into buying lots of the same one. We only ever see one of each Memory Gadget and they're relatively unobtrusive.
It helps that they are portrayed largely as Shotaro's helpers, to compensate for his averageness. Philip and Ryu are badasses so they have one each. What does the use of Candroids say about OOO? I have no effing clue, their depictions seemed largely arbitrary in the first two episodes.
4) You get gob-stoppingly stupid scenes with the Candroids doing things like turning themselves back into cans and stacking themselves or turning into a road in episode 2.
I disliked the Memory Gadgets initially in W but later warmed to them because they could help W's attacks in clever ways and help Shotaro take care of himself when he can't be W. They were useful but never obnoxious.
I don't feel the same character connection with the Candroids that you see from the first episode on with the Memory Gadgets. The Candroids say nothing useful about Eiji or Kogami or even the setting, that I have seen. They are just totally arbitrary.
5) The Memory Gadgets were ignorable if you didn't like them. They just didn't play a major role in most episodes. The Candroids are going to be shoved into our faces constantly judging by OOO's beginning, which means I can't just ignore them at first and slowly warm up to them. I get actively annoyed during Candroid scenes and the direction doesn't let me focus on anything else. It's like the show simply doesn't want you to watch it unless you're going to like the miserable Candroids.
I guess the operative word here is "obnoxious." I am inclined to dislike animal helpers in Kamen Rider unless they've unobtrusive or given something sensible and logical to do. The Candroids are the very definition of obtrusive and I find their role isn't clearly defined. Factor in matters of taste like my problems with the design and I'm just never going to like them.