The difference between Tussauds and Merlin is that, even in Tussauds worst days in the 2000s, they still cared and did their best in the parks in every aspect passionately, and you could tell. Sure, their attractions weren't the best during that era in terms of Thrills, but they damm sure did their best to try and retain the parks magic and charm.
Merlin on the other hand as we currently know it don't have that passionate will. Its either 'Look at our shiny new ride guys!' While also letting the rest of the park rot until they can replace that rotten attraction for another 'shiny new ride'. Not even Disney treat their parks like this, and that's saying something, even their worst and oldest attractions are always maintained in tip top condition in terms of upkeep. Merlin are just way too corporate to run the parks properly.
If I were in their situation, I'd give each park a proper HQ base, with independently ran projects, this can be through TLC groups, Creative teams that can be permanently set there. Money is still the main priority, but also is giving guests the best experience, to bring that magical feel back to them as long as they're profitable or brings in more positive reviews.
We should not be going to their parks having our fingers crossed every time we visit wishing that a specific ride is open or in tip top shape, either through Effects, or ascetic wise.
All in all, Merlin... give the parks more freedom and a little extra budget. That's all... don't focus on only attractions you want to, focus on the ones you NEED to, or let the parks management and staff do so, either through refurbishments, or TLC projects. you'll still gain a great amount of money, but you'll also get better reviews, which is always a good thing, especially for a business. Most businesses want a to leave a good and positive impression on its cleints or guests to make sure they'll come back.