I've been in this situation too when I looked for jobs a while ago. Seeing bad reviews online should be taken with a grain of salt, but also given some consideration. If there are repeated patterns in the reviews, that might be cause for alarm. In one situation, a company I researched company actually laid off a large group of workers so there were many bad reviews; however, that particular department was moved elsewhere and expanded. Many people were not happy about it, and their reviews were written in angry reaction without much thought or composure behind them.
Given that, I have never let that deter me from interviewing or applying for a position at one of the companies I was interested in. No company is perfect, and every individual has different perspectives and backgrounds that influence their opinion. A few reviews online do not give you a full picture of the company. I would also consider what press a company has, its funding, workforce size and demographics, locations, and such. You might end up shortchanging yourself if you make a decision solely based on a few short reviews online, which may be outdated and inaccurate. Sometimes those reviews can be very superficial.
What I found to be a more effective way of figuring out how to gauge a company beforehand is to actually go physically network with people (i.e. meet them for coffee) who are either current or former employees that are either in the same or similar role as you. In a way, it's an informal interview; don't ask for a job outright, but say that you're exploring new opportunities and would like to know what a particular role entails, how the company works, etc. In my experience, people were often very receptive and open to meeting me (nearly 100% response rate vs 0% in online resume submissions) and sharing our experiences and perspectives with each other. It also gives you a better "in" if you do choose to apply for said company. Even better, they may also open you up to more opportunities that they think might suit you.
Regardless, when you do have an interview with a company, that is your opportunity to make sure that you ask them good questions. It's just as much as an interview of them as it is of you. Don't be combative or outright about what you want to ask. Phrase it in a way that is abstracted from any particular reviews, people, or sites.
- How is x at this company?
- What do you (the company) do in situation y?
- How does the company handle z?
- Ask questions about the why behind decisions, direction, strategy, etc.
These are very general and can vary depending on what it is you're applying for. I suggest tailoring them specifically to the company or role. You can also ask your other interviewers the same questions or variations on them to get a more complete picture and see what the company's strengths and weaknesses are. In the end, you should be asking questions and making decisions based on what is best for yourself. It is your job search and life, not someone else's, and you should do what makes you happy.