Right now the Imperial navy is not very competitive or is at least very limited in this regard, this is mostly due to sub-par damage performance in most areas. Intended as the 'most versatile' faction in the game, the IN needs to have, in particular, its weaponry designed with this being the most important consideration.
The two biggest issues the IN now faces:
1. Generally poor weapons damage
The staple macro and lance batteries are supposed to provide the most reliable and effective DPS against almost all foes. Currently, it could be stated that lances perform alright, but macro weapons underperform drastically.
2. "Versatile" IN ships perform terribly and are also overcosted
Certain IN ships have very odd weapon load outs, each filling a very different role. This mix of weapons is fine, except these ships often are over costed and because they only have 1 of each 'type' of weapon, they CAN do anything but they do everything really badly. For any ship to be effective in this game, it has to be consistent in at least one role it fills. The Mars and Oberon are two glaring examples of example 2.
Expanding on point 1.
As a versatile faction, every weapon the Imperial navy needs to be designed to be useful agaisnt certain types of faction, but limited agaisnt others. So the following thought process should apply: (weapons traits) VS (faction traits) = effective/ineffective.
Let me use the two following examples to elaborate.
Ramming/torpedoes VS Necrons
Respectively: (High damage and torps reduce armour) VS (Slow after using jump and easy to catch and hit) = EFFECTIVE
Ramming/torpedoes VS Eldar (any)
Respectively: (High damage and torps reduce armour) VS (very fast/hard to catch and very easy to dodge skill shots with) = VERY INEFFECTIVE
Every single weapon design for the IN should revolve around this general formula (from rams to strike craft to boarding), with at least one weapon type being significantly effective agaisnt one other faction. Obviously other factors need to be considered, like which faction has a positioning/toughness advantage but the general weapons formula always applies, stat tweaks can balance out the nuances.
The current big issue is that while this system does apply to most IN weapons, these weapons are bad or have glaring issues. Macros in theory should work well vs Orks, however their damage is too poor.
IN lances can't compete with Chaos lances, yet IN are too slow to catch them to gain any other advantage and IN macros are actually worse than chaos macros AND Imperial strike craft are so slow and weak they probably won't even apply their damage.
Right now, IN can only compete in matchups where ramming torpedoes are effective, because only ramming and torps stats are good enough.
Expanding on point 2
IN ships that are more specialised (so ships that tout all/mostly macros + torps for close/midrange combat, or ships that tout more lances/long ranged macros for long range combat) don;t perform terribly, however IN ships designed to be 'jack of all trades' ships are awful. I will address the three 'most' versatile ships with the most conflicting loadouts to illustrate my point here, namely the Oberon, Mars and Dictator.
The issue with these ships is that they can do everything, but they don't do anything even half decently, making them pretty well useless, especially due to their nasty price tags. The fix is actually quite simple and there are two options:
Firstly, since these ships have mixed weapon loadouts, meaning they don't have perform consistently agaisnt any target, make them much cheaper so that their weakness is offset.
Secondly, and this is slightly more complex, make each individual weapon a lot stronger, so they can effectively fight any target, but make ship costs high. EG: Even though the Oberon only has 2 hangers, make it launch 3-4 squads instead of two while on Brace/buff the number of assault actions from boarding. Buff the Macros so they do more damage while on reload stance, so it can brawl nicely, and buff the lance damage when in lock on so it can dual with ranged factions effectively. This way, these ships can use their stances to remain effective agaisnt all foes, but they cost a lot, so these versatile fleets are never as numerous. To ensure that these ships aren't an obvious choice over less versatile IN ships, make sure they are appropriately more expensive.
This would greatly enhance the quality and depth of Imperial fleet building.
The Imperial Navy needs some love, and even if it's just general stat tweaks to improve damage it would be helpful for improving the faction as a whole.