LEGO is an adjective. Never call it Legos.
"Dear Parents and Children
LEGO® is a brand name that is very special to all of us in the LEGO Group Companies. We would sincerely appreciate your help in keeping it special by referring to our bricks as "LEGO Bricks or Toys" and not just "LEGOS". By doing so, you will be helping to protect and preserve a brand that stands for quality the world over." [1]
So the singular form is clearly the manufacturer's intention, but "Legos" is widely used in North America and is just one of those words that grates if you haven't grown up with it. For whatever reason I have the same reaction when the Poms say "kit" instead of "equipment".
[1] https://english.stackexchange.com/questions/10839/what-is-th...
This is interesting, and one I’ve never noticed.
Would you say “the drum equipment has been set up” vs “the drum kit has been set up”? Or more in the sense “the kitchen has been equipped” vs “the kitchen has been kitted out”?
US-Americans just get super defensive if they get called out on doing something different than the rest of the world. Sure it is not a big deal and I don't care about respecting the trademark of the Lego company but you can still accept that Legos is wrong. You are free to call it whatever but it will sound very grating to an international audience.
Regardless, it's not an adjective, much less 'always' - it's always a noun; sometimes used attributively ('adjectivally' if you like) / as a noun adjunct, such as in 'Lego bricks'.
[0] https://en.wikipedia.org/wiki/Noun_adjunct#Related_concepts