I’m pretty sure you won’t have any reliability problems with Cat-5 cable doing it that way: the resistance won’t be a problem, the potential danger is that having a long wire like that attached to an input pin on the ESP8266 could cause damage to the chip if there’s a big lightning strike nearby, for example.
That said, I still don’t think you’ll have a problem. What you describe is very similar to how my house is set up. Every light switch is just buttons on the end of a Cat-5 cable, wired back to central light switch controllers. I actually put a 1k resistor in series with the wire to each button to act as a current limiter if there is voltage induced on the wire. There’s more info about my switch setup in these videos: