>So I was looking for a way to "quit food" without the unpleasant side effect of death
You cant, some of our food cravings or at least what we want to eat or fancy are generated by bacteria in the body, some by the environment (heat/cold/light), some by other foods we have eaten, eg lots of creatine will probably create an Iceberg lettuce (phosphorus) craving. So its more complex than that.
Perhaps better to look at what makes you over eat and try to change those situations which could be work, home life, lack of sleep (when tired people always over eat) and manage it that way.
> I'd love to know if anyone has been able to completely replace food with protein powders and vitamins
So something noone takes into account with this approach is the amino acids, vits & minerals are in an easily digestible form, in other words they are not locked up/wrapped up/parcelled up in things like cellulose (plant fibre) and meat cell walls/membranes. If you look at the digestive system, our guts have evolved to break down and absorb certain things at certain points along the digestive system. So people with bariatric surgery have parts of their guts removed which then causes deficiency mainly mineral so they are compensated for with over supplementation or monthly injections.
So my personal approach is eat normal but top up with amino acids, vits and minerals, whilst also being aware of the total calorific intake and expenditure.
Some supps benefit from being taken in the morning, some at night, eg copper, calcium is better taken in the morning because they can have a stimulant effect in the body, and Vit K2-mk4 before bed. Nicotinic acid (reportedly can cause abortions) is best taken first thing in the morning especially if you can hit the gym as it spikes your growth hormone on an empty stomach, but its blunted by fatty foods and it "could" mess up your blood work but it helps break down the cell walls in the adipose tissue (fat under the skin) which is predominantly stored triglycerides. Pantothenic acid (vit B5), shifts fat off organs like fatty livers (massive killer) and shifts it under the skin so its a cheap "cosmetic surgery filler" but it also has a steroidal effect in the body. All the water soluble vitamins are best sipped from a water bottle throughout the day because they flush out so easily so doing a mega dose once a day like a multi vitamin pill is a waste of time when you look at what people pee and poop out from their multi vitamin pill! Little and often.
Interestingly, they have been able to work out that 30mins of exercise first thing in the morning on an empty stomach (only water is allowed), is the equivalent to 90mins after you have eaten something, so maybe see if you can do more exercise as I also think we are designed to eat more calories than we do today but we just dont exercise enough in todays world. The hormones that wake us up are also the best ones for making us more gym buff but then breakfast blunts them and we get all chilled for the rest of the day.
Everything has "side effects" though, so if you did loads of nicotinic acid it will make your bones go soft (calcium used to rebind DNA by the Prostaglandin response) unless you compensated with calcium.
The other problem with all of this is anything recommended will require some form of chemical compensation so before you know it, you have this massive's spider diagram practically encompassing every amino acid, vitamin and mineral.
So something to bear in mind, you have little control over where chemicals go in the body, this is best highlight by cancer experiments using radioactive(isotope) chemicals. One swiss study on Thyroid cancer used radioactive B12 because B12 goes into the Thryoid gland but when they scanned the patient they found it was distributed throughout the body besides the thyroid gland, probably because of the sodium potassium kinase pump (https://en.wikipedia.org/wiki/Sodium%E2%80%93potassium_pump) found in alot of cells. Its not a total free for all chemical mashup because obviously membranes and tissues do influence where chemicals go, but there is still an element of chemical Brownian motion taking place within certain domains inside the body.
Even the form of chemical is important, eg carbonates are generally best before sulfates(sulphates) or chlorides as the latter two can have effects that could be undesirable when taking loads of them, where as carbonates become CO2 which is a stimulate in itself unless you need to sleep.
If you like your food then do your exercise to burn it off instead, go to the gym first thing in the morning, do an Exercise to Exhaustion High Intensity workout on weights (80-90% max weight upto 10 reps no more than 3 or 4 sets), if you dont run, dont bother at this stage the desire to run will come once your muscle mass & skeleton is up to a level and then you will get the desire to run and run and run. Some days I would only do one set, other days I would do 2 or 3 sets, but it was always a sort of exercise to exhaustion, ie get in get the job done and get out as quickly as possible, ie no hanging around in the gym posing and then I would home and have a fry up (cooked breakfast) every day. :) Thats no different to being in the military, ie eat what you like but do the exercise.
This is what I would do every time and would tell other people, but I'm not qualified in anything so do your own research and have an open mind whilst remembering nothing is a panacea.