I have posted on this topic before. I don't know how the big theme parks can justify taking so much of your money and then giving their customers such a shit experience. It's not just the money either, it's the disappointment and the wasted family time being stressed when we should be relaxing together.
I have a 6yo who, unsurprisingly, struggles to wait over an hour in a queue for a 3 minute ride and so, despite having been to Chessington twice, we have never made it onto any of the "big name" rides for kids. Both times, we ended up in the rather unspectacular soft play and I paid out an (additional) fortune for the pay-for activities (basketball hoops, ships etc) dotted around
My children are younger so easier to please I guess (as long as no/small queues!), so we either do funfairs or go to places like Hobbledown, Bocketts Farm, Fishers Farm or railway centres for days out. Things would have to change a lot before we set foot in another theme park again.
And of course the theme parks know that what they offer is shit. Look at the online reviews.
I have a friend who took her 7yo to Legoland for his birthday and they left at lunchtime as it was so bad (one ride the whole morning) and went bowling and for pizza in the afternoon to try to fix the day for him.