I know this Topic of BR compression is being talked about a lot but obviously its mostly talked about Air and Ground, so here is it from the perspective of a Naval/Coastal Player.
Br compression in Coastal is very significant because Coastal mostly goes from 1.0 to 4.0 wich is perfectly reasonable since it hast to fit with the BR of the Bluewater Ships and Planes but there is still more to talk about.
For example the MO-4 sits at 1.0 in the russian tech tree with 2 45mm Guns and therefore is blatantly Overpowered to the point where you can obliterate anything below 2.3. This MO-4 class ships were built and used in the late WW2 meaning that its not just better than other ships at that BR its also much newer. If you go over to the Italian tech tree at 1.0 there are 3 MAS class Patrol boats, these things were built in WW1 and used till WW2. These are comparable to the American PT Boats meaning they have 2 Torpedos mostly 2 Guns in this case its a 20mil and a 50. Cal and therefore are outrageously outgunned by boats like the MO-4.
While this is only the beginning you can see how unbalanced these Matches can become. But at this point there wasnt even an uptier. While the MO-4 is absolutely shredding you lil Patrol boats, have fun playing against 2.0 Ships for example the Pr.1124 with literally two T-34 Turrets on it and steel armor or the british Dark Adventurer with its 114mm Howitzer and another 40mm Gun. If we now take a look back to the Italian tech tree (and yes I will mostly use Italy as a subject because its so underpowerded)
you can see the MS 53, an CRDA 60t class boat armed with two pathetic 20 Millimeter Guns (you can really only use one of them) and 4 relatively slow Torpedos wich you will need because getting lucky kills with Artillery and Torpedos is your only chance at this point if you dont get a Downtier.
If you get to 2.3 this is just unbearable, since 3.0-3.3 is pretty much the most played br of naval since the Bluewater Fleet starts kicking in with your 2.3 Ship no matter how good it would be at downtiers you are going to face Destroyers with 4 and 5 Inch Guns and Coastal Boats (witch at this points are also mostly cannonboats with huge amounts of Mortars and guns) and even the Japanese PG 2 (an Sparviero class Patrol boat built in 1991 equipped with a 2cm Vulcan Minigun).
While you can argue that this only happens in uptiers its undeniabl that 8/10 games played at 2.3 are Uptiers and most of them full uptiers wich (together with the fact, that researching an Coastal ship without Premium at this Rank costs 2 Digit Hours of grinding) just makes it really unplayable.
I myself dont yet have a solutuion for this because it would need a total restructure of the Game but maybe you have one and I would like to hear your Opinion on this Topic (even if you dont have any Coastal battle Experience).