Loss is painful, grief is real, it can be intense. Some people will say "What's the matter with you, it's only a cat, just get another" and that just hurts extra. One might as easily say, "what's the matter, it's only your house that burned down, get another." In my opinion, those people have no empathy and best be ignored, just as you'd ignore a color-blind person's ideas on color combinations - they don't get it at all.
For some people getting a new cat quickly really helps. For others it does not, it feels wrong and disloyal not to give a certain space for grief to burn through.
Every grief is unique, too. All one can really do is live through it. True but not very helpful: time will help. Try to focus on the joys you had and the blessing of love in your life. There is no fixing the past. Do not be surprised by later sudden grief welling up unexpectedly (for me, usually in a very inconvenient place and time).
Much sympathy on your loss. Been there often myself, know how bad it hurts.