That is absolutely true for newbies. They have too little experience to choose to invest in new projects. However, choosing the top altcoins is less risky but means that they will make less profit. Profits always come with risks, so I always advise them to stay here long enough to make a profitable investment.
I do not think that the old projects that are now in the top will all be promising. I do not see the development of many projects and maybe they simply will die after some time. no matter how big their capitalization is.