Ancient is the strongest CT map right now
Meanwhile, Inferno is the T's playground
CS:GO economy changes all the time.
In recent years, offense became much more proficient in CS:GO. Stronger and cheaper weapons (AK, Krieg), easier control of economy and constantly evolving skill of players allowed T sides to overwhelm the defence and make CTs life miserable on certain maps.
Analyzing thousands of maps played in competitive environment in 2021, the best map for attack is former defensive stronghold - Inferno. Only 47.6% rounds are won by CTs which is easily explained by Ts executes onto B and AWP being less impactful on Inferno than on the other maps. Close to those marks between 48 and 49 are Dust2 and Vertigo. Former, in words of Astralis’s captain “gla1ve” is the only map in the pool where you can do the same mid split as attacking side and win a majority of rounds. Latter is still mostly a specialist map, but it got way better for offense after the last rework.
Mirage is essentially a flip (50.2% winrate for CT), which is understandable for the oldest and most popular map, while other four offer bigger advantages for the defence. Overpass, Nuke and Train are known for CT’s ability to lock down sites and casually post double digits at the half time, while Ancient, the newest addition to the scene, is even more CT favoured than Train (54,5% to 54,4%).
It remains to be seen how Ancient is going to look in few months (remember, Nuke rework made map way easier for Ts, Overpass’s meta evolved to the point where attack could simply turn B plant into a deathmatch, etc), but for now it is the strongest map for the defence in the entire pool.