Culture/buy in/whatever you want to call it doesn't always mean you aren't producing on the field. I wonder if the Davis twins, Alex Davis, Eric Lee, Lamar have actually "bought in." I don't think it's a lack of effort on the field with these guys or the person under them being better. All these guys probably have NFL dreams and so they aren't just going through the motions in games and they may be our best players.
I think where the issues arise is in practice and outside of football. Are these guys practicing as hard as they can and pushing everyone around them? Are they holding guys accountable who don't feel like like practicing hard today or going to class or whatever or are they the guys doing it? Do they trust the scheme and coaching or are they free lancing at critical points in the game because they think they know better? I think these are the types of buy in being referred to. The stuff we can't see.
Then you have guys like Tyrin Ferguson, Avery Anderson, Vainuku, Daishon Neal that have in my mind mailed it in and are just riding things out.
Add all that up and it has held this team back at points this year and I think that's where Frost is frustrated.