Limiting screen time is all very well if you have just one child, or two close together.
I have five DCs, with an eleven year gap from youngest to oldest.
The TV (90s and 00s) was rarely off. Oldest DC got a small TV in their bedroom at age 12.
They all played plenty, did chores, did sports, art and crafts, played piano, did hours of homework daily...
I think the problem of 'too much screen time' is actually a problem of 'too much inappropriate content that children can't process'. It's also a case of too many scene changes per second, too much visual stimulation.
I relied on broadcast TV for my DCs viewing content. I never subscribed to cable (Nickelodeon, Disney, etc). My DCs had a great PBS station (in the US) which broadcast high quality, slow paced children's fare (for example, 'Mr Roger's Neighborhood'). Another station broadcast cartoons on Saturday mornings. They watched early evening shows too, as they got older (The Simpsons).
I also bought DVDs for them - all downloadable now. One series my DCs liked in particular when they were younger was a very slow paced series of animated Beatrix Potter stories.
The adversarial themes and elements of programming on Nickelodeon and its ilk, not to mention the blaring ads and egregious materialism, are not suitable for children. But there's plenty of good quality alternative fare.
publications.aap.org/pediatrics/article-abstract/128/4/644/30711/The-Immediate-Impact-of-Different-Types-of?redirectedFrom=fulltext
When it comes to the impact on executive functioning -
Fast pacing is a problem.
Educational or slow paced fare is not.