Can I decline being promoted to Corporal?

You can, but you will be telling your chain of command "I am only in this for myself".

It is not a good image to have, especially within the regiment.

Instead you shoudl, happily, accept the promotion, and use it as an opportunity to learn how to be a better sergeant.

That does not sound like any Ranger I have known.

Go ahead, refuse the lateral to corporal. Then have the reputation for the rest of your time in that you won't step up. It will follow you everywhere you go. Take the frigging lateral, do the job, and take it as a compliment on your potential to become a LEADER. So what, you'd be an E4 team leader. Man, get over yourself, and stop being a whiny little bitch.

So, you dont want to be an NCO, hmm, time for you to go home permanently. If your leaders saw potential in you and make you a corporal, then there are qualities they want to groom you for. But if your about the pay, and the pay comes with responsibilities, then your not NCO quality and recommend you not re-enlist. There are Soldiers out the that want that position and excel to be great leaders. If you do not want the corporal rank, go tell your CSM immediately.

Declining the opportunity to build yourself up is denying the fact that there are obviously people in your CoC that are making the effort to support you and build you up, and may just be the slap in the face that gets that effort and support reconsidered.

TLDR: Unf#ck yourself.

Good question. Because in my head, the question I'd be asking my team leader, squad leader, and/or platoon leader is "if you're ready for me to assume the NCO responsibilities, why can I not receive the pay to reflect that?"

Whether you make the Army your career or leave the military and go into civilian employment my strongest recommendation to you is to never, ever refuse a promotion. You may not think you can handle the responsibility of the position, but there are others - superiors and others that think you can. Accept the challenge and just do your best. The alternative is to disappoint your leaders, and maybe never get another promotion.

What is your problem with th

You have to be kidding. What is the real purpose of this question? While in Germany around 1965, we lost most of our senior NCOs because of the Vietnam buildup with no replacements. I was appointed a Sergeant and placed in a SFC position. I later made SSG and was placed in a MSG slot. The mission had to continue and the junior staff had to step up, and we did. It had nothing to do with pay; it was all about responsibility to the organization and the army as a whole. And think how this looked on NCOERs. If you don’t want to step up then you are in the wrong organization and taking up space that a responsible soldier would gladly do. If I was your CSM you would never be an NCO or get further training. If you want to remain in the army past this enlistment, step up and take the responsibility.

This is largely what happens in the rest of the world. Civilian, Military or otherwise.
Prove you are worthy of the responsibility then the spoils usually follow.

What about all those LTC's filling in Division Commander slots at the beginning of WW2, what about all those PFC's acting as PSG's, and E5's acting as 1SG?

The military is largely a lethargic bureaucratic process of promotions and assignments. You'll find the timing of opportunities don't always line up in nice clean progression of promotions and assignments.

Want to know messed up? How about getting paid less than a younger less capable peer who manages to get BAH with dependents just because he has them. $$$ as a function entirely irrelevant of job capabilities.

How about being an idiot taking command in a O3 slot when only a O2. Getting paid no more, getting promoted no sooner, and taking on all the personal, professional and financial risks of an Active Duty CPT but only paid 1/10th the pay.

How's that for BS?
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It's just part of the system. There isn't a Sr ranking NCO or Officer that hasn't had that situation themselves.

In fact, look up the SPACE FORCE higher officer commands. There is a FOUR STAR on TOP with a bunch of COL's (last time I looked) as direct reports, and they all stuck their necks out in anticipation of picking up one, two, and three stars while filling those roles only as COL's.