The various attribute enhancers such as a the "stimulant" and "strength booster" do not seem to actually do anything.

Eg, I tried the strength booster several times but associated skills such as your carrying capacity do not change at all. So far I have not yet seen one shred of actual evidence these boosters do anything. Also as these, and also all your medkits, automatically magically refill after each mission, there seems to be no point at all in building medical factories, as you never actually need to make any more medical items.
In fact, not only do they magically refill after missions, but if you save and reload they refill DURING missions!

The question is, am I right? Do they really do nothing?

PS/ I have UFO:AS patched up to 1.3

Yes, this game has many bugs and was not finished (devs had work 2 months for free in the end).
Those enhancers, bugged or not, are however almost useless, and they are boring to apply them every battles, so I use none.

Which is a shame, this game could have been so much more.

Sure, I dream about a 'remake' since long.
All good concepts and systems are here, they "just" need to be well made. And the game is not strategically flawed, contrary to better made XCOM:EU.
So good that I still play UFO:AS at now, and will never return to EnemyUnknown.