If you look at expert opinions on decanting, you will quickly see that opinions are divided on this topic. Some experts are in favor of "letting wine breathe," some are against it, and a third group only recommends certain wines for this process.
The famous oenologist Émile Peynaud, who worked for the major Bordeaux wineries, recommended that decanting - if at all - should only be done shortly before drinking. Old, fully ripe wines should not be decanted at all, as the aroma would be destroyed in short bursts by oxidation after about 30 minutes. Other experts recommend this for young, tannic and still fairly closed red wines. It is clear that decanting definitely changes the taste and aroma of a wine, as the also very well-known wine expert Hugh Johnson has found.
The best thing to do is to try it yourself so that you can gain your own experience and form your own opinion. A good way to do this is to take two identical wines, decant one and open the other an hour or two later and then compare.