To add on to what everyone else has already supplied:
At its most basic a convoluted plot is hard to follow and difficult to enjoy, because it requires effort on the part of the reader to understand.
Conversely, the opposite of a convoluted plot is a simple one that is easy to follow, to the degree that it requires no active thought to understand what is happening.
Generally speaking that's why Story Arcs exist.
By focusing on one plot element above all, the story is simplified and easy to follow, or at least easier than it would otherwise be.
While real life can be quite chaotic and many things can come in-between you starting something and the conclusion of that thing, if it happens in a story - especially one that doesn't update frequently - it gets quite hard to follow the story, as it gets harder to keep track.
My recommendation for checking if something is convoluted would be to check where the plot starts and where it ends.
A quick read through the chapters within that range should let you see if there are any derails or sub-plots being introduced that divert attention from the main plot without tying into it at a later point.
If there are no derails or sub-plots like that being introduced, maybe you should look into applying the Saitama method before things go down.
While it's completely and utterly unreasonable to expect a plot of any significant complexity to be summed up in 'twenty words or less', you should be able to manage it in about two hundred words. Anything above that should qualify as being too convoluted to be easily followed, especially if your readers don't read everything in one go and forget details that are relevant to the plot / story.
If heavy strategizing is involved, it might be good to hold a 'planning session' in the bounds of the plot, or a short meeting to see 'if everyone is on the same page'.
Or just a note to 'the dumb one' that's somehow involved in the plan, to remind them of the key points / details to keep in mind.
That way you can remind your readers of all the relevant points the characters involved are aware of without being too on the nose about it.
Generally it helps to have a simplified explanation of the plot (or story elements) to get the gist of them, even if the truth is far more complex than that.
It's not like that's anything new or unrealistic.
Physics has lots of examples where the simplified explanations are partly wrong or misleading, but they are very much enough for a layperson to understand what is going on.
On that note, I think physics is a good example of 'convoluted'. If you want to be as exact as possible, it's going to get complicated really quickly.
Any mathematical proof is highly complex and convoluted, but that doesn't mean the average person can't use or understand the simplified versions / formulas.
They might not understand why they are that way, but they understand how to work with them just fine.
In short:
Convoluted is the opposite of simple.
If a plan is convoluted, it's hard to follow and likely to fall apart on contact with the enemy.
If a plot is convoluted, it's hard to follow and likely to lose readers that don't understand what's going on with the plot.
Streamlining the plot can help reduce irritants and make the reading experience smoother.
Streamlining is either done through cutting out unnecessary parts (as hard as that is sometimes when you actually like what you wrote, but it just doesn't fit there because it fucks up the pacing or diverts attention from the things that actually matter, no matter how realistic it would be for those distractions to appear) or, if there are no unnecessary parts, by reducing the complexity of plans, be that by summarizing them in simple (but potentially misleading) ways or by having someone amend the plans.
That having been said. Choose whatever method you feel comfortable with.
Personally? If it's an important story element, I might just make it something that is also just that complex / convoluted in-universe. Like the magical version of physics.
Other characters not understanding what is going on or what they're being told is not entirely unreasonable. It could even make for some fun developments.
Not everything needs to be simple enough for just about anyone to be able to follow.
It highly depends on what genre you write, but a Battle Shonen is obviously supposed to be much more simple and easier to follow than a Murder Mystery or Military Fantasy story.