Use the National Rail Enquires website. When you find the time/route you want it redirects to the Rail network's website :)
And you get nectar points
I use the GWR app, much better than trainline.
The only way this is true is if the train you want is nearly full ( or its a peak time train that they know will always be full ). Train companies use fluid pricing , so the more seats booked , the higher the price. If you want/need to travel at peak times the price is going to be much higher than travelling in the middle of the day when demand is low. . For example Newark to London in early December .. trains arriving in London in the morning are all £34.50 , but if you choose the train that arrives at 13.30 its only £12.50 ( there are later trains also at this price ). As more seat book the £12.50 price will rise.
You can save on certain routes :) I work on the railway. I’ve seen a few people travelling long distances having spend £300+ on the train line. If they would have went into a ticket office they would have saved £100+. A website doesn’t tell you about railcards you don’t know about/ ways to split the journey to maximise savings.