I don’t view FM as a hi-fi source anymore.
It certainly is for me, Tony, albeit only for a couple of prog's a week. I've never found the Proms' broadcast s.q. to be scintillating, even when I used to watch and listen on my 01 before digital created that time lapse. Sound straight from my TV (i.e. digital) via can amp/pre. is def. second best to what I can get from my tuner but I guess you meant other digital radio sources (which I don't have).
I listen to Music Planet (1600 Sat. aft's, which is a Marmite choice, albeit interesting in a global manner. When they have a group playing live in the studio or even their recordings of (folky) live events like the recent Glasgow one, the s.q. really is up there with other sources. Not sure one would attribute this level of quality and dynamics coming from 'steam radio'.
I've had a lot of tuners over the ages but those were with different systems/locations so not comparable. However, on my current system over the pst 4 or so years I've had 01, serviced 01 (same machine !), Cheapo NAD 402 and currenrly t.o.t.r. Akai from the late eighties. Same 6 element array on chimney and same coax, so comparisons can, I think, be fairly, if subjectively, compared. In true terms, the quality cannot match my CDP and esp. vinyl, but when listening to those occasional quality broadcasts, I'm simply not aware of any uptick when I go to one of my other sources directly after. I find myself continuing to listen to J-Z which follows, and I'm certainly not a modern jazz fan !
Like you, John Peel et el on seventies (and maybe later) radio were not just a delight, but the cause of recording activity on my R2R. Nothing like today then, in vinyl terms and no CD so radio def. was one of the chief sources. However, judging by what little I listen to, the potential s.q. from a good tuner is still very much up there; excluding internet as I've no idea about this medium, let alone experience.