always allocate investment in new coins smaller than your investments in high ranked, reputed coins like btc and ethereum, it's simply basic risk management that despite the fact that your saying is true, still 90% of altcoins could be losing their value easily.
even though it always comes back again with your capabilities of choosing best project out there.
you just couldn't always accurate in your investment so it's better to be safe than sorry, after all even coins like bitcoin and ethereum isn't lacking ROI as long as you have the sufficient capitals to invest in them.