I've just put together a little example from G2's CT side against Astralis on Inferno. It won't be pretty to read but it covers one of the basic flaws in G2's CT strategy.
It's round 4 and Astralis are 4v5 with a half buy (deagle + kevlar, 2 smokes, 2 flashes) while G2 are on a full buy.
Astralis have 3 players in banana and Dupreeh in boiler.
G2 have 2 players on B and 3 on A but decide not to re-aggress on A for map control.
On A, amanek is holding apts, hunter is on short, and KennyS holds library, between them, they've easily got enough utility to re-take top mid (1 smoke, 1 molly, 3 flashes) but they opt to stay in site and give the pistols close-range duels. Instead of the re-aggression needed they turtle up. amanek drops into mini pit to set up a crossfire with hunter who plays from site.
On B, NiKo and nexa also opt not to re-aggress but this makes sense as they only have a smoke grenade between the two of them.
Astralis take top mid and short for free, smoking moto to negate any long players and bouncing a flash off the the hay cart to blind Hunter in the site.
Because it's close range with pistols against a blind hunter and amanek, Astralis are able to take the site with just pistols and get a bomb plant.
The rotations from nexa and NiKo are late as there's no re-aggression on any of the sites and they don't have enough info until it's too late.
This leaves the round in a 3v3 postplant. Astralis pick up an AK and UMP while G2 attempt a retake with an AK, M4, and AWP.
G2 group up towards long in the retake and run in dry, winning all their aim duels. nexa saves his smoke for the bomb which is probably the best way to use it in that situation, as smoking off pit would give gla1ve some more 'cover' to play around and could potentially backfire.
Thankfully G2 win the postplant after putting Gla1ve in a 1v3, but there's no way in hell Astralis should be getting 2 kills and a bomb plant with a deagle + kevlar purchase, two smokes, and two flashbangs.
G2 could've easily avoided this situation had they re-aggressed when the B players knew there were at least 2/4 Astralis players in banana. Dupreeh and co. managed to get all the way up short without any G2 players peeking or picking them until moto is smoked. That kind of map control should never be free as it just leaves G2 no room for error. There's no angles to fall back to or alternative peeks to take, G2 are just forced to win their duels against pistols at close range. It's just not a viable option.