I think this series, alongside the Ashes, has shown that this England side is a good team capable of great results. A great team would have won a home Ashes and, in my opinion, at least not lose in India. A great team would not need the great results because they wouldn't find themselves in so many impossible situations. Realistically the wins in Pakistan remain the absolute best achievement.
As it is, assuming the result goes the way I expect in this test, they've achieved the same series results that they did under Root. There's no question that there's been progress; primarily from a spectacle position. Even though I love test cricket, this team makes it more watchable than ever. It's been a frustrating series because some of those old weaknesses have surfaced but, like you say, India are better and more experienced in almost all departments.
I feel like people think Bazball is some cheat code that has made England a great team when, as I see it, it has just unlocked players to reach their potential. They aren't necessarily better players just more effective. This has been a really good series, like
@Bigby Wolf said last week, it feels very similar to the 4-1 in England when on paper it looks one-sided but has ultimately come down to a few sessions going one way. Hopefully, that's a sign that next time they tour England (although the side might look somewhat different) those who return are better prepared and more experienced to take on the challenge and achieve better results.
India will probably look a different team then too. The series has given really opportunities for some more players to breakthrough. Jaiswal looks like he'll be around forever, Kuldeep seems to continue to improve, Jurel looks like he'll make a very good option particularly if Pant's long-term selection as a keeper is in doubt. Deep looked like Shami 2.0, Sarfaraz has had the chances everyone has been craving for two years. Hopefully Patidar and Mukesh will still be going strong next time England visit.