Enable segwit with no stupid hardfork drama, and see bitcoin skyrocket.
Break bitcoin in half, see the price crash, and see everyone involved in the forked chain going bankrupt, with the price going to 0 on Forkcoin, and with Bitcoin crashing but going back 3 years in price and taking another 3 years to recover.
Your choice.
Except the engineers are the janitors.
Miners get to decide what happens to bitcoin because they put up something at stake (mining equipment).
Developers on the other hand have nothing at stake and thus do not get to decide. Bitcoin would not work if developers would make decisions.
However if miners chose wrong their stake gets destroyed by the feedback of the market (which is controlled by users/coinholders)