They can't degrade bitcoin.

Bitcoin is suffering from the fee problem because it has an huge traffic, not because it's technology is worse then the other coins.
Litecoin and simillar coins may be faster then bitcoin now, but they will suffer from the same problem if they will have to deal with the same amount of daily transactions that bitcoin has to deal with.

More users= more problems, and it's something that the whole crypto world has to deal with.