Regarding the revised thread title, I think it depends what is meant by "simplification".
In some cases, it is a good thing. For example I have argued several times that the WCML IC services would be better off on a 30-min pattern (e.g. 30-min interval services to both Birmingham and Manchester). This would then allow the local services to also follow even-interval 30-minute patterns: last time I checked (in the normal timetables up to 2019) some of the local services on the Birmingham-Coventry and Stockport-Manchester axes were an irregular mess, caused by the insistence on a 20-min service from London. Also, the Euston-Birmingham semi-fasts are a bit irregular too: it always used to be an even-interval 30-min service. So an example on the London-Birmingham axis might be:
2tph IC to New St or Wolverhampton
2tph semi-fast New St via Northampton
2tph slightly slower to Northampton, calling at medium-sized local stations (e.g. Hemel Hempstead, Leighton Buzzard, etc) but missing out the smaller stops
2tph slow to MKC, all from Watford
2tph all stations stopper Coventry to New St
- all at even-interval 30 min frequency.
However, while I would argue for a simple clockface base pattern, I also believe there is room for one-off holiday specials, peak extras, and the like on top of that base pattern.
Some countries such as Germany and surrounding countries manage to achieve some interesting services. The German philosophy (at least that prevailing between 2009-14 when I visited regularly, not sure about now) was to run clockface services on busy key segments between nodes (major Hbf stations), for example Frankfurt to Munich. However beyond the key nodes, each service on each hour might progress to a different ultimate destination, providing a simple service on key busy routes, but also one, or few-a-day through services to other, more far-flung destinations. For instance the two-hourly Munich to Innsbruck IC fast progressed to a different Italian city with each service. The two-hourly Salzburg-Munich-Stuttgart-Heidelberg-Frankfurt was clockface two-hourly on that stretch, but originated from other Austrian cities in some hours.
While perhaps my opinion of this isn't entirely valid as I haven't actually lived in Germany, to an outsider this pattern seems a nice trade off between simple, easy to understand services and occasionals to less-popular destinations.
Perhaps the SWT 2004 timetable change also had it right to some extent (clockface pattern, but with extras where needed) - though it did have some flaws, for example no peak extras on the Alton line; the only peak extra on the Portsmouth Direct was at 1818, when there was also a path available at 1718; peak extra provision to the local stations between Surbiton and Woking was poor, due to a lack of paths; and the peak extra to Winchester and Southampton, at 1748, was a little on the slow side and caught up by the following 1805.
