I have sympathy for Celtic. UEFA are happy to let these mis-matches continue, and even get worse because they are not interested in controlling the mega rich clubs and football will suffer in the long term. You often hear how important it is to be in the CL for all the revenue it generates. But there are certain clubs that are spending even independently of the CL revenue! How can a club that attempts to keep to anything like a proper financial business model hope to compete with such unlimited spending power?
I also laugh when I hear the pundits going on about how noncompetitive the PL teams are in the CL, when the most basic and obvious point is that if a team doesn't have to put out it's 100% strongest team in it's respective league, it will always be strong in the CL. The Spanish clubs don't need to be strong every week, and nor does PSG and Bayern (don't know much about the Italian league to comment on that). What makes the PL great is that there are a lot more competitive games than in those other leagues, so saying our teams aren't as good as those "top" CL teams is not comparing like with like.