I need my Siemens 2 pole 50 amp GFCI breaker replaced for my hot tub but what I bought didn't have the GFCI on it. This is for my hot tub and it's in a weatherproof closed electrical panel outside my home.

Is the one I bought safe and OK to use?

No. You must use a GFI.

Why do you need to replace the one you have now?