Bang-Bang Controls 101
Based on this behavior, I'd guess that the wires are switched. Opening it up, red is connected to R (power) and white is connected to W (heat). Assuming that red is hot and white is neutral this seems to be wired correctly?
Close. These are 24-volt "low voltage" controls. Which means hot and neutral are not applicable terms here, but you're on the right track. The standard wires in 24-volt systems are:
R = 24V supply from transformer (hot-ish)
C = 24V return to transformer (neutral-ish)
W = call for heat
G = call for blower only (in forced-air systems)
Y = call for air conditioning
Sometimes the A/C unit has its own 24V transformer, that's why there's R(h) and R(c). You can see those unpopulated sites right in the plastic molding of your thermostat. B and O are heat pump things.
Back down in the guts of the system, there's an actuator (gas solenoid valve; Taco water valve) that is wired to W and C, completing the circuit. The thermostat doesn't get C unless it is a Nest. Note the spare wire for if that ever happens.
So far maintenance says there isn't a problem. They claim that the thermostat can't maintain an indoor temperature because "the boilers temperature is controlled by the outdoor temperature". This doesn't seem relevant to me, since the point is to control not the temperature of the heated water, but the flow through the pipes into the unit.
You got it. At some "low" setpoint, the thermostat goes BANG! on. And at a high setpoint it goes "BANG!" off. But think about it: A Bang-Bang controlled heater, when it runs, must run hard enough enough to overcome the worst arctic chill possibly expected in this locale.
So in your mind, you are expecting your building to deliver Very Hot water, hot enough to overcome the worst possible Polar Vortex, and on a temperate day of say 13C (55F) you'd run maybe 5% duty cycle. You don't dare shunt R and C (set thermostat to max), or you'd be smoked out of the apartment! That's your expectation.
And.... that's obsolete.
Except the Bang-Bang approach is obsolete. It made sense when gas or electricity was cheaper than smart controls. But now, it's no problem running a furnace at variable speeds - and this enables technologies like condensing furnaces which gain 15-20% efficiency over Bang-Bang units, or VFD-controlled heat pumps which are quieter by a lot.
In this scenario, the furnace runs pretty much continuously at the lowest setting that will do the job. It figures out what that is by looking at outside temperature and from that, estimating how much thermal loss your house is having through insulation and leakage.
In that light, what maintenance said explains everything. Your building has converted to a condensing boiler, which runs the system hot water at a variable temperature based on outside temperature. It is trying to supply exactly the right temperature to your radiators to compensate for thermal losses through the insulation.
So if your apartment had no thermostat at all, one could reasonably expect apartment temperature to follow the weather, but stay halfway reasonable. You can try this for yourself simply by setting the thermostat to "MAX".
However, if that results in an apartment that is warmer than you'd like, the thermostat allows you to do BANG-BANG control of that already-adjusted heat. Because the heat is close to optimum already, the duty cycle will be much longer - say, 90% on a 13C (55F) day.
This also imposes a simple maximum on how hot it's possible to make the apartment.
