I don't see why GTO is necessarily a barrier. Falcon 9 has seen hotter reentries on GTO launches but that doesn't mean it's impossible as the numbers aren't in on what it costs to refurb a landed GTO F9. It's not cost effective for Arianne 5, absolutely. It wasn't designed for it and because it was built around doubling up and sending 2 sats (~11 tons) up at once rather than re-usability. I forget what they called their fly back the engines with wings idea but they put in the time to come up with that for arianne 6 so they are clearly thinking about it. ULA and Ariannespace will become blockbuster to netflix if they don't start playing catch up and fast. Blue Origin still has a long way to go, but at least they are committed to the idea and are farther along than ULA or Ariannespace with landing an orbital booster as far as their tech goes.
Just a comment on this
they could effectively double their amount of launches by launching sats 1 at a time rather than 2, and using extra capability on a similarly designed rocket around reusability. Falcon 9 takes huge hits to its actual payload to land the boosters. It can actually put about 20tons into LEO, very similar to Arianne V capabilities, but chooses to pay the extra fuel towards landing rather than more payload.
As I said though, the numbers for the economics aren't in, but SpaceX is due to launch their first refurbed booster at the end of this month so they are about to be coming in soon, and it's two largest competitors don't even have a prototype for reflying a rocket. It's a pretty huge disparity. It took 6 years of launches to shape F9 into the rocket it is today...not even counting the 3 years of development from 2008 until it's first launch and that was considered fast. If we consider that SpaceX could regularly refly rockets beginning next year, even for a fast and mobile company it wouldn't be until 2028(!) until a competitor would be flying and landing using the same time scale. BO has a headstart obviously, but ULA and ArianneSpace do not.
As easy as they make it look, let's not forget that landing a rocket is definitely not trivial
edit: fact checks if you believe wikipedia. I'd argue that this is kinda moot because they didn't get nasa funding until the end of 2008 to actually start building it. They were so focused on launching falcon 1 to find income that I find it hard to believe they were developing a larger rocket at the same time.
Development of the medium-lift launcher began in 2005, and it first flew in June 2010
Add 3 years to that time line...2031...