It doesn't break down everywhere. This is one of the reasons why BTC is leading the way even though there are a lot of other blockchains which are arguably "better". Being the first kid on the block has a lot of benefits since the mining power is sufficiently large and distributed that it's near impossible to have a 50% attack now, unless the miners stop mining or cooperate.

If you think about it, there are many improvements that could be made to basic networking protocols (TCP, IP, HTTP), but since the standards were set "in stone" so long ago, it is difficult to change now.