yes they are enough dev outside of blockstream...
the rumor that blockstream control bitcoin dev is bc many dev support blockstream goals. But don't work for blockstream.
Blockstream has great power but not to the extent you think. Blockstream has more social power if anything. Blockstream might scare some people but is also trusted by many others...

There is an case study done showing less than 10% of bitcoin core dev worked or held stake in blockstream.