As I see it...
Tyre sizing:
Disc brakes don't restrict the tyre size.
On the OP's propsed titanium replacement for his 853 Genesis, rim brakes would restrict him to 28 mm tyres max, with knock on effects on usable tyre pressure and speed on rough roads or tracks.
Wet weather:
Disc brakes are more effective in the wet.
With rim brakes, there's often a delay between applying the brakes and starting to slow down, which can be dangerous in traffic. If it's very wet, water can get back on the rims as fast as the brakes wipe it off, which is also dangerous (to the tune of a broken pelvis, in what I've personally seen happen.
Rim brakes wear out the rims. The rate at which this happens depends on riding conditions, but I've worn out the rim of a newly built wheel before the tyre that was on it.
Rim brake pads to fit are available in just about any bike shop of any sort.
There are a multitude of different, incompatible disc brake pads, and a visit to a bike shop, even quite a decent one, is likely to fail. That means you may find it necessary to maintain a stock of spares, and take a pair or two with you on any cycling holiday.
Hydraulic rim brakes are unavailable, at least for drop bars like the OP's Genesis replacment.
Future proofing:
The availability of good quality wheels, rims, and hubs suitable for rim brakes is only going to go down, so you'll increasingly be restricted to lower end components.
I've gone disc for my last three bike (one dead, teo in use), mostly based on tyre sizing and wet weather.