JMO but I advise my clients to fix the OTT then get fit. Even seniors in 70's can fix this common malady. As far as equipment (offset and closed face angles) yes it can help some but the swing flaw is still there. Tom Wishon told me back in the 90's that he doesn't design equipment in general for OTT players less offset in equipment he designs and no slice killer designs.
These are just my opinions from a fitting perspective. I run into this swing flaw a lot. On average using cell phone video if a player can see their flaw it is fixable before video to get that idea into a golfers head was very hard. Golfers perspective vs. reality. If a golfer is playing more on the course weekly it's worth fixing IMO but if you are a once a month player probably not but I don't see those kind of players in general as they aren't spending money on better equipment.
There is a large difference in playing a fade without an OTT and cutting across the ball with an OTT.
Example note Trevino down the line playing a fade and taking club out and dropping it in the slot. No OTT there.