I can take or leave foot retention. I've used toe clips and clipless on road bikes, and prefer platform pedals on my hybrids. I've ridden my road bikes with platform pedals and there was little or no difference in my speeds over familiar routes.
Some of my fastest Strava segments and overall times are still from 2017 when I rode my old steel road bike with flat pedals for a few months before switching to clipless.
In 2019 I got a carbon fiber road bike and rode it for a week or two with platform pedals and my usual sneaker/walking shoes. Same results -- just as fast, and I still haven't bettered some of my PRs from that week.
Main reason I still use foot retention on some bikes is for the rigid soles and better arch support. Occasionally I get painful arch spasms riding at full effort just wearing sneakers or walking shoes with platform pedals.
GCN has done at least three videos with different presenters and somewhat different testing methodology and didn't find any significant differences between clipless and platform pedals. None of them looked particularly comfortable with platform pedals, yet the results were about the same.
If I don't use one or the other for awhile -- a couple of weeks or longer -- sometimes it takes a few minutes to adapt my pedaling style to suit either platforms or clipless. But it's no big deal.
I may switch my old steel road bike back to platforms since I prefer no foot retention for urban rides and casual group rides with lots of stops. I'll keep foot retention on my carbon fiber bikes, mostly for the rigid soles and better arch support.