Does the game feel too hard on offensive?

Yes and no. The concept of playing on Offense is daunting, but the maps are fairly well balanced. While there can be a questionable point or two, (like the last point on Zombopolis in some cases) you aren't really gimped for playing on offense - unless your team has far too much dead weight on it.

Bad team composition and skill (or terrible class balance) can make capping a simple point much more challenging than it should be. Nobody likes being matched with dead weight - but it's possible to overcome it. (Although it can be difficult)

The reverse can be true though. Some points are skewed towards offense - like the last point on Seeds of Time and it's overgenerous time extensions for offense.

Time Extensions in general can ruin great defense games as well - nothing's worse than the enemy team barely capping that point in the last few seconds or even well into overtime. The enemy gets a full five minutes or more to derp around with - despite them playing horribly. And if this keeps happening repeatedly despite your team's best efforts, a great defense game can slowly turn into an absolute nightmare.