Sending a CV without a cover letter or with a poorly written one is a recipe for failure. Your cover letter introduces you to the employer and briefly tells the employer that your qualifications are appropriate for the job. Most employers get hundreds of job applications. They don’t have the time to open every attachment and go through every CV. The cover letter tells them which CV is worth looking at. So if your cover letter is not appealing, most likely your CV will end up in the deleted folder without even being looked at.
Don’t let your efforts get wasted. Make sure to include a professional, well-written cover letter with your CV!