A) In coh 1 a player had to choose which tech he should go for since he simply could not afford all of them. That made the far more interesting since the player had to make "strategic" decision in a real time strategy game instead of just microing unit around the map
Factually incorrect.
USF tech worked exactly like current soviet tech, there was no reason to ever get all tiers up.
Wehr tech worked like current, but it encouraged getting every single tier.
British could easily and fast put out all 3 trucks.
PE had decision making exclusively in early game, they got MASSIVE REWARDS and incentives for putting and upgrading all tiers.
B) Reducing the tech costs and making thing available earlier results in sorter window of opportunity for unit to pay back for their investment and in order to compensate these unit are buffed. That in return make the game decided how well these units perform.
This is why units like ultra lights are getting late game utility and ability to vet up through shared vet where they can no longer commit to the fight.
Any other unit can be used in late game without problems, its not always optimal, but its not hinderance either.
Evident of that is the fact WC2020 was so much depended in WC21 and 222 and even result in forfeit when a 222 was lost early.
Top level plays can not be recovered after early loss of any unit.
You lost pios early?
You're fucked and possibly lost.