I know that you're a good player and decently credible when it comes to how Meta Knight operates but just knowing how a character operates doesn't mean you're qualified to make an assessment on a MU that you may have not played at a significant level. I'm not saying that this is the case, but it's just something for everyone reading to keep in mind.
For example, being "light and very easy for Fox to combo" isn't indicative of a bad match up. Meta Knight has the tools to counter Fox's primary approach of nar>shine by using crouch cancel forward tilt, which even at very low percentages leads to a tech chase situation where MK can cover multiple tech options quickly. Fox has a counter to this with drill, which of course, can't be CC'd. But there is counter play, such as shield, or WD back ftilt/dtilt or even run up up smash. Meta Knight's juggles on Fox and his ability to put him off stage and edge guard him are top notch. However, on the opposite side of the coin, if Fox lands a drill, nair, or shine, he can usually convert into a grab or up smash. Putting MK in the air where he has strong aerial follow ups while MK struggles to come down. It's a very even punish game and a very even neutral game. If MK camps at the proper distance, Fox can't even laser. Being light and easy to combo doesn't mean anything. Match ups are determined almost strictly by the neutral game, and MK is one of the few characters who has the tools to counter Fox in the neutral.
As for Marth, there is no such thing as "easily outspacing" a character with a good dash dance. Marth has to rely on his ground game and grabs here which are both outranged by Meta Knight's down tilt so Marth is the one who has to approach into Meta Knight's zone in order to win the neutral. Meta Knight has superior ground speed, superior pokes, and arguably better ground to air launchers, where Marth has a difficult time coming down. Both characters have extremely similar strengths with trade offs in different areas, such as MK having a better run speed, and Marth having a greater grab range. The punish game feels like it is pretty even. And regarding "death combos that are easy to pull off" uh, lol, no. Just SDI and use your recovery mix ups to get back on stage.
And being one of the best MK's on the board isn't saying much, lol.