Some of the best Non-Megas in the game.
Even in the current JP version, they are still being used because they serve a very specific and mandatory purpose.
The Digimon in A tier are very powerful Ultimates. As of now, they are better than some of the Megas.
However, they are A tier because they will eventually be replaced by Megas that do their jobs better.
B tier Ultimates are decent Digimon that you will find use in certain circumstances. Most of them are decent DPS Digimon that are boosted by their Target Plugins. Some of them fill a very specific niche such as healing or status effect immunity. You will use them when you need to but they are not necessary and will be power crept very soon.
Unfortunately, anything else not mentioned here simply isn't worth the bits/materials to train and digivolve them. They are better sold away to collect DigiOrbs.
Good enough for PvP because: