I really feel like that playing (and winning) on Deity is nothing but a conscious decision. Beating Deity does not require any real skill at all as you do not need to anything but follow a set of very simple guidelines. Deviating from basic rules, playing horrible starts and going for speed runs are much different - this is where skills and knowledge take the wheel - but any player who can follow instructions can consistently win on Deity without any real effort and without any exploits.
The recipe for winning a T250-300 peaceful Science Victory is roughly as follows:
0. Pick a good science civ (Korea, Maya for example)
1. Get a decent start (I know that rerolling is frowned upon, but now we are talking about the hardest difficulty of the game. Making sure that you get a decent-ish start (a lux, one or two 2p2f tiles) should not be considered a capital sin - of course, if you get more experience, you will never need to reroll at all.
2. Scout - Settler - Warrior - Builder - Settler and buy a Monument.
3. Plant Pingala in your capital, and move around Magnus around your cities and build all available Science buildings using the boosted chops.
4. Pay some minimal attention to district placement (e.g. place the Campi in the mountains)
5. Immediately send delegations to the AIs and befriend them as soon as possible. Always renew friendships and go for Alliances when available.
6. Build Ancestral Hall, and settle 8-10 cities by T100. If you are lagging behind on Settler production, chop them with Magnus. Settlement locations should be based on the availability of at least a few choppable resources.
7. Build a Campus with all Science buildings and a CH / Harbor with tier 1 building in all of your cities.
8. Send trade routes to good gold yields, and use the trade route bonus cards.
9. Sell everything to the AI (favor, extra luxuries, strategic resources, alliances.
10. Pseudo-beeline Rocketry and after that research everything. Pay attention to Eurekas and switch out of techs that can realistically be boosted.
11. Aim for Political Philosophy, Feudalism, Exploration and Suffrage, use Classical Republic, Merchant Republic and Democracy. Use Science and Commerce boosting cards.
12. Specialize spies on siphoning funds and keep them occupied in enemy capitals.
13. Your gold should be spent on purchasing buildings but you should save at least 7200 gold for a Spaceport purchase.
14. Develop a Spaceport city that has 10-15 pop, 3-4 mines and an IZ (this is usually the capital, but it's even better if you can develop a second city). From the middle game, send all traders from this city. Use Reina to buy a Spaceport, focus on production and complete all space projects.
15. Build Royal Society in the Government Plaza, and use a worker every turn for speeding up the projects. Boom, you are done.
+1. You shouldn't really care for military. Build a few units for defensive purposes in the ancient era, upgrade them for the Eurekas but your defense should rely on your Alliances, not on your units.
I believe that this makeshift rundown can be followed by everyone who has a basic understanding of the game systems - if you have played more than 100 hours, than you should possess the skills for following these instructions. And now I get to my original point: while none of these items are set in stone, going for a Deity victory (at least at the very first tries) certainly limits the players choices and possible actions and requires them to play methodically (do chores). Personally, I think that a fair amount of players are simply not looking for this gameplay experience and therefore do not advance up to the highest difficulties - but they certainly could, if they would want to put in the effort. (I would gladly assist anyone lurking in this thread if they would want to try a Deity win.) Obviously, each of us find different things fun - for some people the fun can be found on King, for others, maybe not on Deity.