So you're saying that Stationary Engineers & staff are being phased out due to modernization & automation of equipment. Ok we'll go with that.
Why on earth are you dead set on entering a field that you know you're being phased out in? I can't say I see the logic in that.

How many buildings have you been involved in the commissioning of? How many ceilings have you poked your head into only to see duct work missing, access panels that you can't open, thermostats in the wrong spots or missing, things wired wrong, units not even being close to being calibrated because a sub was thrown off the job, do you want me to continue?

It's easy for you to sit at your computer and assume that a brand new, state of the art building will be nothing short of perfection. But until you deal with it first hand, you have no clue. I have no issue working in an old building. If the staff there is good, most of those issues have already been dealt with.