From a game design perspective, is there a reason these features exist?
The cost these things incur is marginal, maybe 5% of credits gained in a match.
Do repairs get brutal at high rank?
Is this just a remnant of a once completely overdone feature that made repair costs brutal?
As for manufactured ammo, I’m not sure when someone would deem it necessarry to equip these. Any ‘close calls’ or outright failures are the fault of the pilot and team, not a marginal difference in ammo.
This is the 7% that ammo adds to your normal damage:

Totally worth it, right?
Repairs are just a small credit sink developers put in the game for lord knows what reason. They do get harder to deal with in higher tiers, but if you’re losing more money on repairs than you gain by playing, it’s probably a good idea to go to a lower rank with less punishing costs to learn the ropes.
Ammo is like a custom modification slot for each weapon. At lower ranks, you only have access to the damage boosting one, which is still pretty good. 5% is basically the entire difference between a mk. 1 gun and a mk. 5 gun, so don’t dismiss it as useless out of hand. Especially since you’re dealing with ships that have 20,000 nominal health, without factoring resistances. 7% may not sound like a lot, but it saves lives – and ends them.
Of course, the ammo situation changes really drastically at rank 7ish. There, you get options. Options like a 30% damage bonus for a 50% range penalty (curved reflector for thermal weapons), or a straight 10% crit chance bonus (shaped charge shells for kinetic weapons). On top of that, you’re making more credits per game, even if you lose. Credits start becoming a thing that is measured in millions, not in thousands. Progression slows down so that the net income from single games stops mattering quite so much. The end result is that ammo becomes a large boost in effectiveness for a small cut in income – something like 2%.
Then you reach the manufactured ammunitions. There’s two different kinds for each damage type. One is a (better than normal) straight boost to damage, and the other fills a niche no other ammunition fills for that damage type. Spread reduction, overheat improvement, and crit chance increase, for kinetic, EM, and thermal, respectively.
Now, the straight boost to damage is pretty nice – it’s got something like a 2% advantage over the normal damage boost ammo, which is, again, about half the difference between mk. 1 and mk. 5. The materials used to make them is also pretty common. For instance, I have over 1000 silicon in my inventory, without particularly trying to gather it. A less active player might have something like 300, easily.
On the other hand, the unique manufactured ammunitions are a really, really nice thing to have around. Shrapnel cannons and mass drivers (event weapon for frigates, devs likely won’t make it available again for a long time) can benefit really well from spread reduction. Every thermal weapon ever benefits greatly from increased crit chance – although ion emitters and beam cannons stand out as being incredible with them. And eclipse launcher and singularity cannon are very hard to use without either a shared cooler or the heat reduction ammunition. The materials used to make them are still really common, too!
So, tl;dr: Repairs suck, but ammo is a lot better and cheaper than you think.