If Karl Marx were alive today, he would still say that the working class is exploited in industrial societies today.
Marx would start by looking at truly industrial economies like the one in China. These economies, unlike the US economy, are still based largely on industry rather than services. Marx would note that there is rampant inequality in China. He would note that the rich are getting richer while the workers remain subjugated. This would not give him any cause to rethink his ideas.
Even in a much more affluent society like the US, Marx would still see exploitation. Here too, he would point to the tremendous degree of inequality. He would argue that the fact that executives make so much more money than workers shows that they are extracting surplus value from the workers’ work and keeping it for themselves. He would also point to the continuing loss of manufacturing jobs. He would argue that this was a result of the capitalist classes constantly seeking profits without regard to the way their actions impact the workers.
While it is indisputably true that workers today are better off than those in Marx’s day, he would still argue that there is plenty of exploitation and would see no reason to revise his theories in any very important ways.