I also mainly use a watch for time and date. Extra functions do not necessarily make a watch less reliable, but using those functions means requiring more energy.
If you want a watch that requires very little maintenance, go for a solar powered watch. The con of such a watch is that the rechargeable battery probably isn't easy to buy and replace, but the pro is that it takes a long time before battery replacement is necessary. On the watch forums I've read that the rechargeable batteries in the Citizen Eco-Drive watches should last at least 20 years.
Casio makes solar powered watches too and they also make watches with so-called 10 year battery technology. On the watch forums there's a periodic discussion of which is better. Some say rechargeable batteries are not as strong as 'normal' batteries. But I know too little of this.
Mechanical watches require more maintenance. They need periodical service. The mechanical components of these watches need to be cleaned and oiled to run properly. An advantage of being mechanical is that you don't have to worry about electronics and the availability of suitable batteries. But periodical service can be expensive, especially if the mechanical movement is complex. A simple hand winding watch that only tells time takes less time to service than a complex automatic watch with extra functions like a chronograph or moon phase indicator.
Mechanical watches are also less accurate than quartz watches. But if you don't mind adjusting the time a few times a month, a mechanical watch can last you a life time when serviced well. The Seiko that I inherited from my grandfather is from 1967, but is still running strong.
If all you use the watch for is telling the time and you don't care very much about the type of movement, I recommend getting a quartz watch which is solar powered or has a long life battery. After those 10 or perhaps even 20 years, decide if you want to replace the battery or just buy a new one.
One of my G-Shocks has a tough solar module and a wave receptor module on board. It gets energy from any light source and adjusts time by using a radio signal from an atomic clock. It always sits near a window. So whenever I grab it, it tells the correct time and is fully charged.