Benettton might not have even got the Renault engine if Senna lived. Once Senna died the 1994 grid had no champions on it and the driver with the most wins had about 7. Renault decided to align with the sports new star.
With regards to "new cars, new tyres, new this", I read this a lot and history has shown with major rules changes change very little. The only subtly change is the better drivers become a little better initially.
2016-2017 - no dynamics changed between team mate pairings that remained the same.
2013 to 2014- no dynamics changed between team mate pairings that remained the same.
2008 to 2009 - no dynamics changed between team mate pairings that remained the same.
Quick drivers have always remained quick, Senna was probably the most adaptable driver of all time. The first time he ever drove an F1 car he was quicker than Williams' race driver within 10 laps. He went from Lotus to Mclaren and was quicker than Prost from day 1. The same when he went from Turbo to NA, the gap to Prost grew. Then when gadgets went onto the cars he stayed at the same level as he did when they were abruptly removed. The only time he ever drove an Indycar he was on the pace of the current line up within the first hour or so.
Top tier drivers do not suffer with rule changes, they never have and never will. The only driver that ruins these patterns is Kimi Raikkonen who also ruins the "drivers always do better in the 2nd season when joining a team" pattern too. He is very inconsistent and fickle with his car, why he isn't a top driver. He didn't even ever race road/ none single seater cars but beat an all star grid at the 1984 Mercedes S class event at the Nurburgring with pole and the win.
Having written all that, the cars barely changed from 1994 to 1995 anyway

it was not a major rule change. The engines went from 3.5 litre to 3.0 was the biggest change in terms of lap time which does not affect the actual driving at all, with the engines losing about 60-80 BHP. The difference between a Mercedes and a Honda currently, 1-2 seconds per lap.
People also say, Senna was getting old. He was the same age as Damon Hill who battled MS in 1995 and won the title in 1996. He would have also been 2 years younger in 1995 than Prost was when he won the title in 1993 and 3 years younger than when Mansell won his in 1992 who was driving cars 4-6 seconds per lap quicker than the cars of 1995.
Hill should have also easily won the 1995 title. He won 4 races in 16. Collided twice with Schumacher when trying to overtake him (i.e. he had the pace to keep up and try overtake him), lost another 1-2 races by spinning off and lost another 1-2 due to reliability. Hill himself had the speed to win about 10-12 races that season.
He actually drove a really good first 7 races that would have been 4 wins and 3 2nds if not for reliability issues and a strong championship lead. But it was the remainder of the season that he blew it with his driving and the car was reliable then too.