If every combat is dragging and you're not seeing any part of your rpg playing as acting ... maybe there is a connection. If you, as a DM, are not infusing character into the combat and you're experiencing drag in every combat ... while many DMs I've worked with in 5E are not experiencing drag in 95% of combats and are adding personality to the enemies in the combat, I'd suggest you're not taking advantage of all anti-drag tools.
I have played many 5E games for a decade, and a decent number under 2024 rules, and I have not been experiencing drag as a player or DM except on rare occasion where a particular monster build and a particular PC design just result in a slap fight. That probably accounts for 2% of combats. If I'm not seeing it, despite a wide experience with many DMs, it must be an avoidable problem ... and seems unlikely to be the default state,
Regardless, 5E is designed to run about 10 to 13 combats per level if you follow the guidance in the books. Most DMs shrink that number by having tougher combats. If you run 20 levels with 12 combats per level, that is 240 combats. You can add tempo, environment, and other features to combats without repeating them in those 240 combats, especially as you get tools to be more diverse as players advance in abilities and gain the ability to adventure underwater, in the air, through the planes, etc...
If the monsters surviving longer is causing tedium, it could be that you're not making the encounters themselves interesting enough.
If it is the plethora of options that is slowing down combat, I'd suggest working with players to give them a more succinct view of their capabilities. I often provide players that struggle with analysis paralysis a succinct sheet of player that lists the core abilities of their PC without all the rules language embedded. It works for me.
You could put it in one $125 book or five $27 books. You could sell them in book sets to keep it at three purchases. The fear of five bindings, while perhaps a cool adventure title, is likely not as relevant as one might think. Separating them physically allows them to be used at the right time in the right way - allowing you to put training books to the side while you have only reference materials in books that get handled at the table.
Characters in a setting are in a story. If you do not grow the story through crafting and effort, it is just a bad story. The story is what adds purpose to the game. That purpose, and the PC interaction with it, is what players tend to remember looking back decades later. They forget (most) of the critical hits, but they remember when they realized their long time ally was a vampire, that the MacGuffin that the paladin was seeking would make the paladin (despite a lack of preparedness) into royalty, that the ally that had been helping them from behind the scenes was not only a famous hero of old ... but one that had become a mind flayer.
This is a main difference between BG3 and other 'RPG' video games. The storytelling is masterful compared to rivals, with great acting, significant impacts from the choices of PCs, and meaningful progression through a narrative that culminates at the end of the campaign ... and then breathes with epilogue to slowly release that connection that grew throughout the game.