Obviously large organisations don't like ideas...

You work inside a large organisation.  You have a great idea which you tell anyone who will listen but nothing happens.  Obviously large organisations don't like ideas...

Or maybe not...

If nothing happens with your idea, perhaps you need to sell
And by selling I'm thinking of SPIN selling.  For the people you need to influence to progress the idea:

• What is their (as opposed to your) situation?
• What are their (as opposed to your) problems?
• What is the implication to them (as opposed to you)?
• What do they (as opposed to you) need? And how does your idea align with this?

Is it surprising that people are typically not interested in ideas about problems that they don't believe is relevant to them?  Is this really limited to large organisations?

Ideas have different sizes and types
Some ideas are easy to do and don't impact a lot of people.  Other ideas are quite expensive, require a lot of coordination, and impact a lot of people.  It seems reasonable that the way we deal with the idea should depend on where it is on the spectrum of difficulty and risk.

Perhaps the reason why the idea got stuck because it was routed incorrectly?

Or... the organisation's idea routing isn't reasonable and only has one route for all ideas...

There is always an existing system
There is always an existing way that ideas are handled within an organisation.  It may not be explicit, it may not be altogether effective, it may not even be consistent, but it does exist.

With a smaller organisation, you should probably still notice problems with how ideas are handled even if it's not an explicit approach.

With a larger organisation, this is highly unlikely.  Making the existing approach explicit and encouraging curiosity can help highlight the problems.