This is no different than saying that most people who are new to trading stocks should just invest in bluechip stocks like Apple, Facebook, Google, etc instead of getting into penny stocks. Basically the top alt coins or bitcoin are obviously more safer because they have been around longer so the chances that they pull a 99% loss is slimer, however they are still possible.
One thing to consider is this. One time a few years back when BTC was $1 or so, it was also considered a risky penny type stock investment, however if you invested then at $1 you could of made $20K per coin that you bought. Hence this is the reason why many newbies invest in risky small cap altcoins. They invest little like $100, so if it goes to 99% loss they don't lose much but if the alt-coin gets a good exchange listing like Binanace and ends up going up 100x then the pay-off will be big.
So the conclusion to this - depends on what you want from crypto investment.
If you want to understand the market, to be able to trade short, you are willing to learn a lot (or you just want to put in money in long term and not to lose a lot) - you should invest in top alts/btc
If you want to play in crypto lottery - then invest in high risk altcoins and wait for the miracle