In a human versus human campaign, running out of population to man your industry is a significantly greater issue than running out of materials. At least, that's what I've found - I've always hit the population crunch first, provided corundium and duranium are locally abundant for me to get exponential growth going. Which is why I tend to focus on having an industry that can support more firepower per million people than one that can do so more cheaply. If you choose not to research production-boosting techs then that's your own choice, but shipyards will end up outproducing your factories by a factor of three or more. That kind of tonnage advantage can't be beat. I don't particularly care about gallicite costs as only engines use that resource - from my perspective, it's free materials that I can't use for anything else anyway. If components are pre-built, especially engines, you'll find that the construction times for ships are sliced by a factor of two or greater. And as for wealth, that's what the economy-improvement techs are for.
I don't require a perfectly homogeneous fleet - I'll build new ships as tech advances, re-purpose the older ones into supporting fleets or colony defences, and retire the oldest ships. I've found that about fifteen million population in military yards is enough to replace an entire fleet in under a decade. And I do build ships to doctrine, it's just that I have little in the way of shooting wars going on till I leave Sol, so there's just no need. It'll obviously be different in a human versus human campaign, especially in a single system start. Another factor to consider is that yards can be transported by tug, and are actually fairly small - a 10,000 ton yard with four slipways shows up as a 80,000 ton contact. Compare that to the mass of fighter factories that'll be manned by five million people - about 2.5 million tons. Yards are far easier to shift around, so shipbuilding is, to an extent, protect-able. And for an Earth start, with sensors on hand, anything manufactured on the planet will get instantly detected and logged, so hiding a ship's existence is impossible and masking it's broad signatures gets difficult.
Also, passive sensor missiles locking at ~20 million km will be within the range of anti-fighter missiles. The platform is definitely getting shot at. There's also the issue that with sensors, your missiles get worse per - 0.5 MSP of sensor could be 0.5 MSP of warhead, or armour, both of which will assist in penetration against well-defended targets while sensors do nothing.
I also fail to see why a fleet with superior speed has a necessity to hide. Once the faster warships are underway, fighters will get two, maybe three strikes before the slower carriers fall behind and lose range. An interesting tactic with this would be rushing a fleet past an enemy force and blockading the jump point on the far side of the system, cutting off access. Any attempt at throwing missiles will be defeated by simply jumping to the next system then jumping back, making the missiles lose lock and self-destruct.