The kind of "consulting firm" you describe here is what we used to call a body shop: it is basically an out sourced HR department for temp workers and anyone working for them needs to keep that in mind.

As one of their "bodies", it is wise to think of them as an outsourced marketing arm rather than an employer, whatever the formal legal relationship. They do the client search for you so you can have more time to do the actual technical work you enjoy. You always have the option to find someone else or even develop your own marketing and business skills so that you are not so dependent on them.

To me an "employer" has a responsibility not only to pay you a salary, but also they often have a career path in mind for you. Since they can't fire you easily, their best option is to develop you. A temp firm/body shop can easily fire you so it has no motive to develop you. If one works for such a company one has to take the initiative and plot out a career path of one's own. No one needs to be a victim if one does that. Spend some time looking the market and industry power dynamics. Brainstorm about what would give you more negotiating power. Is it skills, professional network, exposure and self-branding? You aren't going to get quarterly reviews asking how you've grown professionally from a body shop, so you'll have to do it yourself.

I think it also worth pointing out that there is another very different kind of "consulting firm" that does actual software consulting rather than shopping out people. There is often a special area of expertise or methodological approach that colors the company's projects. The company looks for projects that are large enough for employees to work together as a team. There is usually training and knowledge transfer. Even though most of the work time may be spend on site at various clients, there is still a sense of company and team. Employees who are not on a project usually get assigned an in-house task. They don't get fired just because they are "on the beach".

My own work experience has largely been with this second type of consulting firm. I've been both on the service provision role (working at client sites) and also in the management role in such companies. I found a lot of advantages to this sort of environment: projects are constantly changing so you are always getting exposure to new ideas and technologies. You also get to experience a lot of corporate environments. At the same time, you have a group of people who care (somewhat) about you and your professional development.

They come in large and small sizes. I've never worked for Accenture, but I believe it operates that way. That would be an example of a big firm (a very big one). There are many boutique firms that also work this way. If one wants to work for such a firm, it pays to network aggressively. The boutique versions of these firms aren't the sort to take out big ads in the weekly tech employment section of a newspaper.