Re: Genuine question
You couldn't make it bigger and build/keep it in the UK, there aren't the facilities big enough.
However it is big enough to have catapults and arrestor gear fitted so that's wasn't the issue. There were issues with the untested nature of the equipment that would have been fitted, it's only just entered service on the Gerald Ford. Additionally when it was said the carriers should be built 'for but not with'* catapult equipment that was a bit vague so BAE just left lots of big spaces under the flight deck, when they were asked to actually do it the cost estimate rapidly went up, presumably because they had no expertise in the matter.
Conventional carrier aircraft aren't as much cheaper as you'd think if you look at total cost of ownership, the F-35C version isn't that cheap anyway, but even with the F/A-18E which can't carry as much as an F-35B from a carrier, it's hampered by the requirement to return to the ship with a greater fuel load to allow for missed approaches. You don't get missed approaches with a VSTOL aircraft so the F-35B can return with less fuel in reserve. Conventional carrier aircraft also take a lot of abuse in the take-off landing phase so tend to wear out at a similar rate to VSTOL ones, there's actually a limit on the number of carrier launches and recoveries they can do before they're restricted to land bases.
Although there's a valid argument to be made for having better enabling aircraft, e.g. tankers, AEW, etc. realistically the MoD can't afford to add more aircraft types to its inventory anyway.
*A lot of UK defence equipment is like that.