Best of England 2025

If you're referring to the Best of England tours in 2025, a review of the daily itinerary (you can find it on the tour page, as well as the other England tours) shows that it does not go to Blenheim Palace. However since the tour ends in London, you could easily add on extra days and take a day trip out there. You might also want to look at a day trip to Hampton Court.

Note that the 2025 tour has a revised itinerary - Blenheim Palace not included next year.

The OP is specifically asking about the 2025 tour, which does not include Blenheim Palace. The description of the tour and what’s included can be found here;
https://www.ricksteves.com/tours/england/best-england-tour

It appears that the itinerary has changed for 2025. Blenheim Palace is no longer listed under the "What's included" section and the Day 4 description no longer mentions Blenheim Palace, and has been replaced with a visit to Oxford.

2024
Day 4: Stone Circles and the Cotswolds
This morning we'll take a walking tour through Avebury's mysterious prehistoric stone circles. Then we'll drive north to Blenheim Palace, touring this gilded mini-Versailles that was the birthplace of Winston Churchill. We'll end our day in the charming, flower-boxed Cotswolds market town of Stow-on-the-Wold.

2025
Day 4: Stone Circles and Scholarly Oxford
This morning we'll take a stroll through Avebury's mysterious prehistoric stone circles. Then we'll drive north to the college town of Oxford, home of the oldest university in the English-speaking world. We'll join a local guide for a walking tour of the historic center and learn how the town has been shaped through the centuries by its university and rivers. We'll end our day in the charming Cotswolds market town of Stow-on-the-Wold.

Having looked at the 2024 itinerary, you probably wouldn't have had a lot of time for Blenheim Palace anyway. (May be that is why it has been removed?) It deserves at least half a day if not a full day! I would agree with the suggestion to extend your visit at the end to visit Blenheim Palace. You could also include near by Bladon where Winston Churchill is buried.

I took this tour in 2022. It included Blenheim Palace. I was not fond of that place, but I was also not fond of the Palace of Versailles when I took the Best of Paris tour. I would much rather have gone to Oxford.

I do agree that the time allotted to Blenheim was very short on the Best of England tour I took in 2022. I was particularly looking forward to seeing Blenheim and the guide mainly took us on a walk through part of the gardens & then turned us over to a guide to see the state apts. I was having a problem with a pulled hamstring and didn't go on the walk, but spent my time in the Winiton Churchill museum on site and loved that. I love Oxford, too and would suggest you start or end your time in England there and go to see Blenheim as a day trip. Or you can, of course, take the train from London to Oxford at the end of the tour and make it just a day trip.