I made this exact mistake when the Switch OLED came out. I got caught up in hype, I bought the new one, and slowly it dawned on me that I just spent 300 extra dollars for exactly the same machine I already had, and a screen that, as good as it was, was NOT worth that 300 dollars.
If you don’t own a Steam deck, then go nuts! Do what you want.
If you already own a Steam Deck, you already own everything you actually wanted a Steam deck for. An OLED screen is not going to make the games you already play somehow magically better. You’re fine. Chill out
You don’t ‘need’ Steam Deck at all. You don’t need to play video games (shocking).
BTW I was happy with my Switch OLED purchase despite having a V1. Screen is one thing, it was an upgrade across the board - just like Steam Deck. I will be upgrading to Deck OLED as well probably.