Honestly, I think CTF was an eye-opener in some ways. It's a mode that positively screams for bunkering down, especially if you've got any kind of a lead. Defense is a major component and can't feasibly be ignored.
And that results in games where both teams bunker down while they poke at each other, which is boring as hell for everyone involved, and probably way worse for any spectators.
I don't have any real issue with the faster pace; if it becomes an issue in terms of hero usefulness, there's a few tweaks you could make to certain heroes to improve things; take Rein's move speed reduction while shielding away, for instance, or at least most of it. If a shielding Rein is more mobile, he can react to dives more quickly without being left out of position or having to drop the shield to get back in fast enough; it also means the entire team can move with him at full speed as he repositions, without leaving the safety of the shield. As it is now, the fight can just pass Rein completely, meaning he has to drop the shield and (typically) Charge back in, all of which leaves his team unprotected. With good communication, that's not necessarily bad, but without it, it'll likely mean people get killed.
Roadhog being able to move while healing (but not shooting while channeling it, for obvious reasons) is another possible tweak. I think his nerf left him a little weak, and boosting his survivability might be enough.