You said "better than" not as well as.
I honestly don't get why anyone would think not signing Ronaldo is a failure on our part. United have committed £75m in fee and wages for someone who is still going to be on their books just shy of his 39th birthday. Why would we be stupid enough to better that offer? Not only that but going forward is one part of the pitch where they have some decent options whose progress he's going to block. The only thing that's annoyed me about him ending up there is the endless crowing about how it's going to turn them into title contenders, but that'll make it all the more sweeter when they fail. It's yet more reactive business from United and it never works out well for them.
There isn't an endless supply of strikers who would improve us. We wanted Kane, we couldn't get him. As a plan B, carrying on with the squad that's apparently so glaringly lacking that it won the league and reached the CL final last year is better than wasting £40m on a category B player just to spare our transfer team's blushes.
I agree that the addition of a striker is an obvious area in the squad that needs to be addressed but if there's nobody available right now you can make the case that it's probably smarter to keep our powder dry for now. People saying that our recruitment is shit and people need to lose their jobs is way overboard. We've had more hits than misses over the years and just as importantly, our about to retain world class players is second to none.