It's totally acceptable as long as you write for credible websites that don't have spammy content and don't do link trading. Even well-known websites like Moz and Mashable regularly feature guest posts.
When it comes to guest posting, here are some things to keep in mind:
1. Write guest posts only for those websites that are relevant to your website. This will ensure that you get quality backlinks from a relevant website. For example, if your website is about healthcare and if you write guest post on an automobile blog, it won't be of much use for your website SEO.
2. Begin with small niche blogs in your industry. Once you have published 3-4 guest posts, use them to pitch your guest posts to bigger sites like Mashable
3. If your website is a local online business, it's important to write guest posts on other local websites in your industry, even if they are not high authority. When it comes to SEO for local business, relevance is more important than domain authority.