Brown is significant because he caucuses with the Republicans. This could put Republican chairmen in all the committees, so that the Republicans determine what legislation comes to the floor.
This is far more valuable than any vote on legislation. Anything that doesn’t get to the floor won’t pass, even if Brown would have joined the Democrats on it.
There are more than enough vulnerable Democrats in red states and states trending Republican that will be defeated to give Republicans control of the senate.
All the presence of RINOs do is force the Republican leadership to cave and pander to them.