Very fun theme park There is a driving school where you can drive small cars on the path and it has sea life and the park also has a toilet in the park.

Went with a primary school aged child and it was amazing, Went mid December and there were no queues, it was such a huge difference to the other major theme parks.

The other thing to mention is the legoland hotel, which I'll separately review, but the themed rooms, while pricey, are an absolute treat if your child is really into a specific Lego theme (e.g. Ninjago).

A wonderful time for children and adults alike.
Went on a Friday and Saturday. It got a little busier in the afternoon, and it was busier on Saturday, but never too many people and was able to get on most rides with either no wait or within around 5 minutes. The only exceptions were the boat ride in the Lego City section, which took 10-15 minutes, and the submarine on Saturday which took around 10 minutes. How busy the park is likely depends on the time of year, however.
There is so much to see and do inside the park, many statues made of Lego and little details here and there. I am sure I didn't see everything, despite 2 days spent in the park. Had a great time on all the rides, especially the submarine and dragon rollercoaster. Miniland is very interesting, and again has lots of little details, many humorous, that awards those who spend the time to stop and look at everything.

In the park, there was a fun and exciting atmosphere the entire time. Each area has its own look and background music, which makes each area distinct. Lego City is especially impressive.
The staff were all very friendly and welcoming. Although everyone has masks on, you could tell they were smiling.

I have seen complaints about the prices in the park, but I found most things to be either reasonable considering the setting (and no more expensive than at a normal café/restaurant outside the park (but not as cheap as a family restaurant)), or even cheaper than I expected (at least some Lego sets in the Big Shop were cheaper than I have seen elsewhere). Vending machines are priced a little higher than normal, but you are allowed to take a bottle in with you, so I recommend bringing your own and then using a vending machine if needed. Go to Legoland expecting to spend money, and you'll not be disappointed.
The only thing that I believe is overpriced are the carnival games. They are too difficult for small children, and the prizes didn't look like anything special, so for 500yen it is, in my opinion, a waste of money.

One small complaint is related to not being allowed to bring in carts or large bags/cases. I understand it, and complied by keeping my case at the hotel or in a locker by the park entrance. Upon entering the park with a case which I planned to put into a locker straight away, I was told at least 5 times by different staff members - all around the entrance who could probably have seen each other - that I couldn't go around with a case. That's fine. So, it was a little annoying to see people in the park with carts and cases. If Legoland reads this, please do a little more to enforce your rules inside the park, not just at the entrance.

So as not to end on a negative note, I'll repeat that Legoland is a wonderful place, with a lot of fun to be had. Go there prepared to spend money. Two days was not long enough to see and do everything.