Turks can do many more strats besides Fast imp (and anyway you rarely attempt this outside of Arena)
Welp, technologies that reduce a unit stat are an AoE3 thing, and anyway those Cavaliers would still be well above average (only FU cavaliers and Paladins would be better) for a price of 60+75*1.5 = 173 food, which is slightly less than 2 hussars. This would be waaaaaaaaay too strong.
So a Turk farm would end up giving 250 food. Besides the fact the +25% food is a chinese rip-off, this+food costing farm would radically change the Turks from the “manage your gold civ” to the “I need just 1 res civ”, which is boring.
But Sipahi is a Castle age tech, and Artillery in Castle would be useless.
Those crappy +20 HP is what allows them to kill all other cav archers besides War wagons and Elephant archers. But unlike those, the Turk HCA is still super fast and can use his bulk to raid for longer under arrow fire. Not to mention for Turk the LC is auto-upgraded so that you can easily combo them.
I’m pretty much sure they never got pitted against all European countries together. And they had tons of gold, one reason being that they had control over trade routes from South and Eastern asia. It’s much better historically than say, no crossbows on Spanish.
I’ve tried to find what Soliman did to the system but it’s mentionned no where, even in the Turk version of the article (https://en.wikipedia.org/wiki/Timar) And still according to this, the system was likely abandonned because there were too much people and not enough land to give.
Or you can use your faster gold mining speed for archers, and then in castle it helps for Xbow, knights, camels, mangonels, CAs, monks, and technologies. I’m not going to pretend their eco is top-tier material but it’s definitely better than actual bottom tier civs like Goths or Vietnamese.
Compared to Spanish and Byzantines they look weaker but compared to Portuguese and Viet (other civs with bad early game and good late-game) they are much better. Also, if we take into account high level 1v1s Arabia on Voobly (https://aoestats.io/stats?elo=2000%2B#?orderby=win_rate), which are a really harsh place for late-game civs, they are actually really close to Spanish, and almost at a 50% winrate, which is balanced. Of course now there is DE, that buffed some civs below the Turks in this list… but it also nerfed Spanish by making tower rushes weaker.