Fair enough on everything except the bit I've highlighted, there's no real excuse for not leaving your house early enough to get there for when the gates open.
Depending on where you live, that can be easier said than done.
For those living in Staffordshire or another fairly immediate locale, getting there early is probably not that difficult.
If you live further away, though, getting to Alton Towers early varies between difficult and nigh on impossible. I, for instance, live in Gloucestershire, less than 10 miles from the South Wales border. It takes us 2.5 hours to drive to Alton Towers on a good run and sometimes 2h 45m-3h on a bad one. Our routine get-up time for a trip to Alton Towers is 6am, and the car usually doesn't even enter Alton Towers' property until at least 9:30-9:45, with us not arriving at the park entrance itself until gone 10am. For us, arriving at the gates for 9:30 or whatever is impossible unless we stay on site or in the local area.
For people living in more extreme parts of the UK than I do (extreme probably isn't the best word for it, but think of places that are far north, far south, far east or far west), getting to Alton Towers for opening time would probably mean rising at the crack of dawn or possibly even leaving the night before.
As for the monorail itself, I very rarely take it to the park these days. If we arrive as early as possible (which we normally do), then it's usually already got a huge queue. I personally find the walk to the park perfectly fine.
With that being said, I do speak as a fully-grown adult who walks around 2-2.5 miles per day to get to and from university (My walk from Cheltenham Spa train station to the University of Gloucestershire comes out at a bit over 1 mile in each direction on Google Maps). I can certainly imagine that folks who struggle with mobility, or folks with young children, would struggle more with it. According to Google Maps, the walk from "Theme Park Car Park" (a locational marker pretty close to the start of the pedestrian path through the woods) to "Corkscrew Track" is 15 minutes, or 0.7 miles. If you're walking from a car park further back, this walk can hit 1 mile.
A lot of resort guests don't use the monorail as they can use the Galactica entrance, though admittedly that's a long walk from the back of enchanted village. Day guests only use the monorail if they're in the main car parks (including J). Before EV and the sheds were built there was also a lot of grass parking beyond the hotels that would have used the monorail but now anyone using overflow parking will walk.
Capacity is probably around 1200/hr these days. On a medium-busy Saturday (say 12k people on park) I'd expect around 2/3 of guests will walk in. The monorail could probably carry twice as many people with more trains and faster boarding (either with gates or just relaxed rules)
Wow, is the throughput really only 1,200pph these days? That surprises me given that the theoretical is 4,100pph... did the ride ever get this figure?
I know 1,200pph is a very respectable throughput (it's roughly what Nemesis achieves on full capacity), but given a theoretical of 4,100pph, as well as the sheer demand that the monorail gets, that does seem quite low.