Since stonehenge? Hell I designed it
I've been in hobby 25+ years and to me its about simplicity via automation and reducing unnecessary operating expenses with a future goal of a nearly self maintaining tank. I still use a 3-4"sand bed, refugium, lots of rock and ozone but most else above and below has changed. I run a calcium reactor and kalk mixer (via ATO) combo that takes care of calcium, magnesium, strontium and alkalinity and maintains a steady 8.2-8.35 PH range with it. 10# Co2 lasts me at least 6 months, Caribsea reactor media mixed with KZ magnesium lasts close to a year and all are reasonably priced. The Kalk mix is very cheap and I don't have to constantly be forking out cash for 2|3 parts or some other additives. IMO dosers and just about anything that needs to be dosed are obsolete but remain a lower cost startup while costing more long term. Vodka/vinegar dosing would likely be the exception but for the price of most good dosers you could buy a biopellet reactor. I'm sorry but if your dosing nitrate/phosphate somethings wrong. People go to extremes to eliminate the two and then have to add it back. Try feeding your fish and corals more.
In the process of going to a recirculating bio pellet reactor that will eliminate all sorts of things I've tried like carbon dosing, Aquaforest pro bio s, GFO etc. Years ago I even built and used a homemade carbon denitrator. The only real maintenance cost is occasionally adding more pellets as they wear. Nitrate and to a lesser extent phosphate has been my nemesis since my first tank. I've always used GAC but eliminated it mostly trying to heal a tang with HLLE and prevent it in others. Eventually I may go back to GAC using a high quality pelletized carbon.
Manufacturers and businesses love all the high markup "systems", additives, snake oil and other boutique items to keep you constantly spending money on consumables. I may keep a few things on hand but really you should not need much more than salt, amino's if you have SPS, some sort of coral vitamin additive and maybe a trace element product (water changes should handle that if you change water enough or use AWC). I'm now using Aquaforest aminos, coral V and I use Pohls coral vitalizer. I've tried a couple other AQ products and they won't be continued. If you hadn't noticed overpriced KZ is striking back at AF with 25% off products at least at BRS who does not sell AF.
As far as fish a few meds, variety of frozen/flake/pellet/nori/live food, selcon, garlic and some dried plankton mixes enjoyed by fish and corals alike.
For skimmers (that some will argue are not necessary) all I'll say is that things are SO much better now than my first which was a Saunders airstone driven skimmer and later with a Saunders ozone unit that always broke. Some of the others I used later like red sea etc. were not much better. Current is a Ozotech that has been in use 2+ years now w/o issue.
For flow less return flow (~5x) and more in tank flow via power heads. For a 200g I'm running a 1585gph Waveline DC6000 at about 90% power and my current reactor and CaRx are fed by it via manifold. Had mine running 24x7 2+ years now and no issue. The newer ones they really screwed up. One of the most burdensome tasks I did years ago was manual topoff. A good ATO made tanks so much less work and added stability.
Lighting ugh... I've used everything from regular fluorescent, HO, PC, VHO, T5, MH and LED and I still don't know what I want. I started this tank about 2 years ago with a new 6ft MH/T5 and it was great as it had been on previous tanks. This time around new issues related to heat and power in my new house so I switched to 5x Kessil A360WE's. It solved the issues and lowered my E bill but not really all that happy with coral color/growth. I've been pondering resolving the MH issues and to going back to my old fixture or maybe even a new one. IMO I think the hybrid's with T5/LED are the future but not sure the LED setups in the units available are there yet and aren't controller friendly. Like with my MP40's LED's offer the modern feat of being fully controllable and having programs that do different things at different times of day.
Good controller with redundancy for critical systems like heat and ATO! All I'll say is I've only ever owned Neptune from Aquacontroller II on.