Is carbon dating a farce because it assumes rate of decay has remained the same over thousands of years? Not to mention initial amount.

No, it's not a farce. Yes, it is based on an assumption. Yes, it is limited to 45,000 or 60,000 years depending on the lab and method. It is also reported that lightning can reset age indications to random numbers, and lightning has often played a big part in Earthly history.

What do you suggest instead?

50,000 years is the average limit: older samples don't have enough C14 remaining.

But it's possible to get more accurate dating with other methods.
Nitrogen and flourine absorption dating are good for bones.

Fossils are dated with radiometric dating using isotopes of uranium base by counting the neutrons in atoms.

U–Pb or Uranium–lead dating, can datedate rocks formed from 1 M to over 4.5 B yrs old within error margin of 0.1–1%. percent range.

Other radiometric methods use Samarium-noedymum, Potassium-argon, Rubidium-strontium, Uranium-thorium, Chlorine-36 and others.

As far as I know, no one has tried to mine Element 99 for this purpose.

Possibly.  But its fun!

It's for real.