Before you drop money on a new bike, wha is wrong with the old one? Is the bike the wrong size? If not,you can replace components to make it comfortable. Nice new comfy saddle, different width handlebars, different brake levers. seatpost setback, length of the handlebar stem, width of tires, air pressure, rims, for example.

My wife has an 84 Bianchi road bike that she considers very comfortable after some adjustments. If you go to a bike shop, they will set up the new bike in a position that makes the new bike comfy. Who knows, maybe the old one can be set up too?

I know plenty of riders that ride old bikes that are comfy but set up properly. Now if you want something lite and fast, that's understandable but will cost plenty.