If one can't walk 500 m, then public transport is unlikely to be of much use. Metrolink stops were planned on the basis of potential passengers being willing to walk a slightly longer distance (I believe 800 m, but stand to be corrected). Other tramways have shorter distances between stops, e.g. the Blackpool tramway has 38 stops over a distance of 17.7 km.
As for bus service withdrawals in Greater M/c, there are now significant areas with reduced or no bus services both near and well away from Metrolink. Many frequent long-established services have disappeared over the last 50 years leaving main roads without any bus service, or with one that is of minimal use due to roundabout routes and low frequency.
Examples of key routes that have been withdrawn completely include:
ex MCT 62 Chorlton to Heaton Park - there are now no bus services along Withington Road/Yarburgh St in Whalley Range
ex SCT 73 City centre to Heaton Park - there are now no bus services along Leicester Road going to the city centre
ex MCT 75 Greenheys to Heaton Park - there is now only 1 hourly bus along Lloyd Street to Greenheys
All of these routes were former tram routes (other than the extension of the 62 from Yarburgh St to Chorlton). Cheetham Hill Road/Bury Old Rd are now served only by the 135 Bury-M/c service (every 10 minutes at best), with a re-routed 59 as far as Halfway House.
The former NWRCC route 125 from M/c to Glossop via Denton (which ran every 15 minutes) has also disappeared, leaving virtually no buses between Hyde and Glossop.
I suspect you are slightly exaggerating the figures to prove a point, as the DSS (or whatever they are called this week). OTOH, I think the average distance on Metrolink outside the city centre is 1km, but don't forget people have to get to the main road in the first place, often from extensive residential areas. Blackpool is a "proper" tramway, even with the new fangled trams, which at least are more comfortable than Metrolink. It also pre dates De-regulation by many little short of a century and there is full integration of fares with the buses.
Your history is also slightly selective, given that the N/S examples you point out are self evidently pre-SELNEC. The 135 is registered at "frequent intervals" and is generally every 8-9 minutes on Mon-Sat daytimes and every 10 for most of Sunday.
The 125 was obviously undermined by the heavy rail link to Glossop, but also a more general policy of reducing Limited Stop services with the growth in congestion during and after Deregulation. There were, of course, numerous other Limited Stop services along Hyde Road - albeit mostly peak only.
Obviously, over the years, bus services have reduced as a result of lost patronage - a vicious circle - but this has had its peak periods of 1986/7 (obviously) and the last 3-4 years. The point about Metrolink is that many routes based on the supposed Jobs hotspot of Manchester Airport, Wythenshawe and even Sale along with numerous parts of Oldham and Rochdale and to a lesser extent (so far!), Droylsden have all seen significant reductions in services, with Arriva virtually wiped out.