"Carrot of profits"

Donkeys may be encouraged to undertake forward motion either by hitting them on the rear end with a stick or by dangling a carrot ahead of their front end. Hence the expression stick or carrot means to offer either punishment or reward to those we would wish to act in a certain way. In your example, the prospect of profits 20 years down the line is presented as being akin to tempting a donkey with a carrot.

Simplified, the sentence becomes:

"Using the carrot isn't likely to sway VCs."

The carrot is essentially an incentive, shortened from the metaphor, "the carrot and the stick."

What the sentence says is that VCs of smaller companies--who are looking for a quick profit and exit in perhaps just three years down the line--cannot be swayed by the possibility of profit (i.e. the carrot) 20 years later.

It means reward as in the phrase "the carrot and the stick", which refers to the use of a carrot as a reward and (hitting with) a stick as punishment for a horse or other draft animal.