speaking from my conversations with @LordVincent on workload and the like,
1: working full time on these things makes a massive difference. where you probably just have your free time to draw, many creators with featured comics are working full time, 7 full days of drawing and writing time - and yeah, a lot of the time, 'like a machine.' making comics full time is a lot of work
2: batches!!! the first way to speed up your process is to work in batches - five pages sketched, then five pages inked, five pages coloured, five pages lettered. i used to make one page a day, and therefor two pages a week. now that im working in batches i make five pages in 2-3 days. i know vincent sometimes works in megabatches - smth like 50 pages sketched, then 50 pages inked, etc, within a tight timeframe (two weeks or so?)
3: theres lots of little methods and shortcuts to working faster, and professional comic makers utilise many of them. you can find lots of tutorials on youtube on ways to make the process faster, and you can be looking out for your own ways too - for example, i like having hatching in my work for texture, so im always looking out for new hatching brushes that make the process faster.
working fast is key to making comics professionally, and its a skill you can absolutely learn