This is interesting to think about for sure. I completely agree that the meta of CTF maps has become incredibly stale due to the midfight strat and druids being as slippery as they are. It's to the point where WSG and TP are honestly extremely boring to play for me, and I used to love playing WSG. I can only really tolerate 3-4 games on queue nights before I log out. However I think that problem is caused way more by the current meta as opposed to druid fcs.
Obviously rdruids are the best fcs by far, but even if they were banned and we forced people to use other fcs, im not sure a whole lot would change regardless. The strategies to get the flag might change slightly and teams will probably need to provide more support on flag picks, but at the end of the day controlling midfield will always provide your team with a massive advantage in flag play, and there is literally no way to play around it.
If one team wants to play mid, unfortunately you're playing mid too. Offense/defense strategies and any other form of splitting up your team loses every time to a team running around with everyone together the whole game. It's simple, just all about having the numbers. To an extent, turtling in your own base once you actually get the flag somewhat "counters" a good mid team by forcing them to split a bit of their team up (at least 1 healer with fc) but I'm pretty sure everyone agrees that turtling is even more boring.
Anyway, without a druid fc, the team that wins the initial mid clash has the freedom to just collapse their entire team on the opposing teams fc (and you'll know exactly where he is because he can't stealth) after both teams pick, and this is the reason why currently a druid is essential.
Mid fights are the cancer that is ruining CTF maps, but unfortunately I can't really think of anything reasonable to get rid of them somehow. You can't just tell people not to fight in mid or something.