Historically, plenty of people have gained more rights through actions that were far short of an actual revolution. For example, it would be naive to say that the suffragette bombing campaign didn’t at the minimum accelerate when British women got the vote, but killing four people and wounding twenty-four isn’t a revolution, and women getting the vote moved political power to a group that previously had effectively none. Initially, the only women who had the right to vote were property owners or the wives of property owners, but the same act of parliament gave non-land-owning men the right to vote, so it was specifically transferring power from the Bourgeoisie to workers, too. Clearly, power can be transferred from the Bourgeoisie to workers through reform.

There’s a perfectly legitimate argument that there may or may not be a limit to how far this could go, e.g. whether there’s a threshold minimum amount of power the owning class can tolerate before further reform becomes impossible, or whether if it’s done in palatable increments, reform could continue indefinitely. It’s an unfalsifiable argument, so whether or not it’s true, the only way to know is if it’s done successfully, and until then, there’s a first time for everything might apply (although you could try and fail a whole bunch of times and end up with an upper bound on how easy it might be).

Personally, I think it’s a decent rule of thumb that if you’ve got enough people who agree on the same position to make a revolution successful, you’ve got enough people to get an equivalent government elected if you’re in a vaguely functional democracy. Taking over an existing party or forming a third party that dwarfs all the others should need about the same amount of the population as battling against an incumbent government and any other factions that want to be the last ones standing after a revolution. If you’re not in a democracy at all, then obviously a revolution is necessary, and sometimes a self-described democracy isn’t one or isn’t working properly, so needs some kind of push in the right direction, but if you’re already in a democracy, and not winning elections, a revolution’s likely to backfire, especially as the type of person most keen on using weapons against humans is the same type of person who’ll always put their own needs above the needs of others. Getting loads of people to agree with you is the biggest hurdle both for successful reform and successful revolution.