There are a LOT of freelancers on Upwork who are Excel experts. Many who provide ONLY Excel services and are very successful freelancers by doing so.
MS Excel is one of the very vast field. You can not imagine how Excel can help you in daily assignments. For a freelencer it is not necessary how good you are at Excel but the good thing is how good you are at problem understanding and solving. for example . If my boss give me data of 100 items and ask for detail regarding each item . Now its My intelligence to work it with some reports and vlookup or query it one by one. In both cases my boss will get same result but time is one of the most expensive thing in life. if you are good at problem solving your cognitive level is good . you understand what job requirement, how it will complete, what are the outcomes, time boundation, etc all things matter. So have a seat, sit calmly, read job, write proposal, verify payment, job history, freelencers coments, discuss it when receipt invite, lisen them when they complete, reply them and if any sugestion, must share as they can satisfy with you and remember you for next job . etc.