Just about 150 years ago, all the major ragas of today might have sounded really "folksy" by comparison. I have heard some of the Sangeetha Sampradaaya Pradarshini versions of Dikshitar Krithis and see how the treatment of ragas of the Dikshitar school differed dramatically back in the day to Thyagaraaja's or others.
Here a few points to start off :
There has been an explosion in gamakas in the last 150 years or so to where it is now and it's still evolving. The influence has come from various vocal and instrumental influences. Thodi for one is a raga that evolved gigantically to say the least. Compare the old Desiya thodi to the current Hanuma Thodi.
We can also the Ariyakudi style vs Semmangudi or GNB and you see the evolution for yourself. However some also aver that the gramaphone records forced musicians to cut out some gamakas so that they could sing fast enough to fit within the tape. This also caused an evolution of the average listeners' attention span to around 6 min or so.
Interestingly, even in the same vocalists, look at the records in the 1920 and 1930s and then see the same by the 50s and 60s. I will probably recommend the GNB centennial collection as a prime example of a vocalists' evolution. There is also a cinema video of MLV singing Entha Veduko which you can compare to the later MLV.
Madurai Mani Iyer's style of singing is especially unique as it is actually an older style with less (or only essential) gamaka focusing more on simpler melodic beauties and some short approximating brighas where heavy gamakas would be used today. For eg. p,dp m,pm g,mg are used where today we would sing DP-PM-MG. This device goes back to at least the trinity period. Unfortunately he was probably the last of that kind.

ATaaNa for one is still evolving and the Antaara Gaandhara note seems to be becoming rarer and rarer.
Khamas added a N3 at one point courtesy of Mysore Vasudevaacharya. Veena Dhanammal added a M2 in Paras, but this didn't catch on like Khamas did.
Listen to the Jagadodharana of Raja Iyengar with that of M S Subbalakshmi. There's another.
The Hindustani influence in many CM ragas and vice versa and the import and export of ragas.

Abheri. Enough said. That wasn't as much of an evolution as it was the loss of an original raga altogether and personally I think that is something to be avoided. At the moment there are 4 different ragas being labelled Abheri out there.

Maanji and Bhairavi have nearly become the same raga and the jury's out as to whether they were indeed two versions of the same raaga.
Many ragas that Annamacharya composed in don't exist today.
Gowda Malhar, Mohanakalyaani, Karnaranjani, --- all just over a century old but almost immediately settled into their identity.
GNB created a few ragas himself -- Amrita Behag, Shivashakti. The story is Amrita behag came out of some really vakra phrases that TNR attempted in Kalyaani which inspired GNB to turn them into a full fledged raaga.
BegaDa changed so much over time that in a music academy lec dem, PSN said that variability was the only constant in that raga.

Vivadis are still evolving. No one explored them to that level of individuality as much as Thyaagaraja did in his time and all later composers' efforts were still in pursuit of establishing their identity (Personally I think he himself created 60 or so ragas unique to him). I think Rishabhapriya at some point gained a distinctive identity in the past century.
For all the things that purists may say, evolution is still happening. The Dwi madhyama ragas are a prime example and from my experience with Suryashree, I don't understand what's this idea that 2 madhyamas cannot come in a raaga when Sindhubhairavi is the leader of that lot.
Might I add all the fine tuning that Veena Dhannamal carried out on varnams and krithis? Or how many vivadi krithis of Thyagaraja have been retuned in other ragas?
And now days you have started hearing some chord progressions at some points in ragas and swaras in instrumental concerts.
Evolution is the bottom line.
All those interested to chip in with their insights are most welcome
