Can one combine four patterns, while staying relatively subtle…?
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Nice pattern on the suit - are the shoes Vass?
This isn't a pattern or color failure, it is a contrast failure. The very bold tie stripe, pocket square, and shirt all have the same tone. Change the tone of any one (stripe, shirt, or ps) to a much darker tone, and this outfit would work very well. Some changes would be better than others.
Allowing the ps to match the shirt is a good move, but not when the tie stripe is doing the same. A navy tie with burgundy or even a deep red repp would fix that. Even a yellow repp on navy without the blue line would work, while being just as bold as your present tie, if not bolder
If you keep the tie, then the pocket square needs to be solid navy if you wish to keep it blue or maybe better still a dark brown, burgundy, or red tone with at most a hint of light blue in the patten. Better the blue in the pattern be navy to pick up the tie and not light blue to match the shirt.
You could change the shirt to a midrange blue or robin egg hue. I think even a navy fine line shirt could work, but it would be very tricky to get it right.
If you are really bold, try a red or burgundy fine line shirt or even a red candy stripe, this would be more tricky still but it could be awesome in effect. Although, this might defeat your purpose of matching largely blue accessories.
I might also recommend that you minimize the impact of your present shirt with a waistcoat/vest matching the jacket or a cardigan that is noticeably to substantially darker than the shirt. If you do this, you would still need to tone down the ps though to at least a medium or royal blue.
If you think an outfit is to matchy or clashing, think contrast failure first, and change the tone of any one of the clashing elements, before you give up entirely on your proposed composition.
Just my opinion. YMMV.