What you wear to work matters because, while this notion is not always overtly evident, the existence of an office in a world where capabilities can otherwise be converted to working from home indicates intentional separation from home life. This obviously is not the only reason for the existence of the office, but this is the main point for why what you decide to wear matters as you enter into that context of being separated from home life. The office is an intentionally designed space to foster higher levels of synergy that remote work cannot otherwise achieve. It is a space designed with professionalism. That professionalism, while required in the building, does not necessarily need to come home with you. The office helps bring work-life balance.

If it was a fight to be casual before, it is a norm now. Throughout the pandemic, as employees have worked from home, meetings have gone from in-person real observed body language to lagging facial expressions where the mute button was either accidentally left off or accidentally left on for the millionth time. Collogues no longer see more than the collar of a shirt which has afforded people with the opportunity to wear whatever is comfortable.
I hope you are picking up on how sloppy this etiquette has become. Many employees will return to the office with a blasé attitude assuming this new ethic as the norm, they may even look down to realize they are still wearing fleece pajama bottoms.

The opportunity here is to not take that mentality back to the office. Your boss will be going from seeing that you have an online status and presumably working, to actually seeing you in real life, working. How will you differentiate and prove to your boss that you are committed to your context?
If you are dressed like it’s the weekend, it projects the persona that you wish it was the weekend.
Show your boss that you want to be there. Clothing is a great way to fake it ’til you make it because even if you prefer to be working from home forever, you are wearing clothes that show you are committed to the moment that you’re in which is in the office working hard.

A recent Bloomberg Newsweek cover displayed a picture that was a metaphor to the evolutionary image of an ape becoming a homo sapien, where the cover was the evolution of the work from home professional. The employee starts hunched over (like an ape) squinting at his computer screen to working from home. Where at first he doesn’t know what to do with himself to the point where he has even stopped shaving. Eventually, he evolves like the ape into a homo sapien going from that painful squinty computer to a standing desk wearing professional attire on top and fleece pajamas on the bottom. He has arrived at prime work from home professionalism balance. The article itself goes on to explain that this may be the new normal.
Remember: If your employer is asking you to return to the office, do not let that be your new normal. The status quo is going to be to bring that lifestyle back to the office. You will not stand out. Realize your context and understand that casual is not appropriate for the office. (There are exceptions but we are not discussing those companies).

To conclude, when you look good you feel good. Even if you are partial to wearing comfy casual clothing, sticking to this mentality of dressing to impress will bring you more confidence. And honestly, you should feel confident knowing that you are truly contributing to making a positive impact anytime you go beyond the status quo.

Come away from this with an understanding that the leaders that have influence over your career, NOTICE.