Certified

Ahem.

In another cartoon, Pigpen walks through a park sandbox, and literally sucks all the sand out of it as he passes.

A/K/A The first season of The Umbrella Academy.

This is so very much like the response I get when offering non-DnD games to prospective players...
 
"How about D and D, but like _this_ instead of that?"
 
(Where "this" usually means 'my favorite character type levels up thrice as quickly as all others, is immortal, and has access to all the magic, all the time.')
 
 

In addition to @Scott Ruggels great advice I might add a step 1.a that might help bring things into focus. 
 
There are a lot of great superhero games on the market. Each of them do things differently, and offer a different experience. Give as many as you can a try from Capes to Truth and Justice and see if these meet your gaming needs. If not, why not. Develop a list of things you want to see in your spandex, that you are not getting in other games, and try to identify what you can do differently to bring that experience to people. 

So, a few things to keep in mind, you cannot copyright mechanics. This is one of the things that made the OGL amusing to me when it first rolled out 20+ years ago. If you want to write a D&D clone and use everyone mechanic they have published you can do that today legally. What you can't publish without authorization are specific terms or setting material. 
 
Your statement implies that you want to shop your game to a major publisher. I think the big question here is, why? We live in a age where print on demand is no longer a bad thing and major PDF distributors have crossed over. Conversely, there are games like Misspent Youth that was self published, popular, and a major company approached the author afterwards to pick up the IP. 
 
Full disclosure, as a self published game designer, these are questions I've asked myself. From when I first started publishing in 2013 to today, things have only gotten easier to go it alone. Yes, get something legal done before going to Kickstarter. At the same time, that shouldn't stop you from play testing in the slightest. 
 
Also, if you are worried about promoting material, it hasn't been an issue for me so far. Which reminds me, I need to update my signature on this site. You can also get links to specific Itch products I've produced from the Free Adventure Seeds threads. A lot of them are only published as blog posted, but over the last year or so, I've been doing full PDF releases and linking to those. 

https://www.shudder.com/member

Re: Generation X - A Metahumans Rising Adventure A new arcade hides the Eisenreich's return and their plans to corrupt and control the youth. Uncover the truth, and save the teens drawn into Happy World.   https://housedok.com/re-generation-x/

Spoiler Alert!