Depends on context of your goal, which is omitted in your question. If you are just creating some small venture of buying a .co or other ntld with backlinks, then sure go with another extension.
However, If you are planning to name your company, like a real company, with incoming email and the .com isn't available it would be a better decision to change the name to something that is available in .com- just as the name has value as is with any other short or one word .com being parked for the last 20+ years from a domain investor(s).
Why not an alternative extension? Lost customers and customer confusion is the reason as .com is the default in the vast majority of people's minds so you will lose traffic and potential visitors if you try and create a company with a .co, .xyz, .world, .online, etc. I often type in a domain name .com only to see it is parked, then need to search and discover it's another extension like .io or .ai. Not everybody is persistent in finding you and could just skip off elsewhere instead of doing a search for your extension.
Another aspect is if you build out on a .co or .xyz, etc, and become very successful the person who registered and controls the .com will ask for a lot more money for it if you decide you need to switch from .co to .com. People who invest in domains look closely at all prospects, and even if you look at using a proxy buyer they will figure it out.