To stick with the theme of Dungeons & Dragons, would you say that you cannot enjoy the game as a player since reading the Monster Manual and DMG? That makes an assumption that you have done so, but I think it's safe to assume you've done some DM'ing. Personally I don't find that my enjoyment of the game ruined from a players perspective, despite having much of the MM and DMG content memorized.

Some people think that metagaming and power gaming (min/maxing) are wrong in the D&D setting. If I only knew what my character could know I would tend to agree. The truth is that I don't actually know everything my character would, unless I make my character a total rube. I'll use an example which hopefully is a good comparison to this situation.

In the new 5e module "Curse of Strahd" there is a background that was introduced to 5e through the module. My friend was DMing and was hoping one of us would take that background. Knowing what that is like from his perspective I elected to take it, even though some other backgrounds might give me better combat perks. As I was paging to the part of the module that I would need to copy that info from I saw a sword that is available to the players depending on which cards the Vistani Fortune Teller draws for the party (one of the features that give this module extra replayability). I couldn't help my curiosity, I read what the sword was and what it does. Perfect for the character that I'd made, it got me excited. This module is designed to be tough to finish. Anyone familiar with the Ravenloft setting (and perhaps Barovia) knows that the 'Devil' Strahd is no pushover. All it said as to the location was somewhere in the Svalich woods. The Svalich woods are a pretty big place, so I decide to keep my eyes peeled any time we are in them. As luck would have it, the fortune teller draws the sword as one of our fated items that can help us fight Strahd. All of this is meta knowledge that I'm technically not supposed to know IC. This knowledge did not ruin my enjoyment when it came to finding the sword. I wasn't prepared for the difficulty of the encounter that put it in our hands, I didn't know any of the tricks I might use to make said encounter easier, nor does the information make our end goal any different than before we knew of the sword. All the information did was to tell me that this is a sword I want, and as well that I should be looking for it in the general vicinity of Svalich woods. Finding the exact location of the sword was still necessary, as was figuring out how to acquire it (I'll keep that part spoiler free, just in case anyone is looking at playing the module). Indeed the only thing that I knew is that I could find it in relative location X, which wasn't a big spoiler because it meant that I was very attentive every time we went to the woods (which was several times for different reasons), which actually slowed us down because the first bunch of trips were totally unrelated to the sword. That's alright, though, because we found some other things that we might not have.

Now, for the most part I can agree that spoilers in general are not something I enjoy, like social media plot spoilers, but all at the same time not every type of spoiler truly ruins the experience. When I ask people IC where to find something in game the vast majority of responses are basically a walkthrough of how to get there and where to look. "N e s s s w e, open desk, get all desk. Go up and sell it" which is way more of a spoiler than the item db telling me that somewhere in troglodyte caves there is a decent starter piece for a minotaurs horns. I had to explore the caves to find the horn tips, whereas the made up example directions (which were meant to mirror an actual location that was given to me in game) were instant gratification directions that didn't enhance my knowledge of the area beyond those exact locations. I personally would prefer to have just a bit of direction and go looking for myself. Why the direction? Why not just go out and explore those areas anyway? Well, because I have done that in some places only to find out four hours and five mob deaths later that there isn't anything that I can use, or the stuff that looks good I'm not able to get and I have no idea what level the stuff is to come back for later. Bonus, any levelling progress that I had made has been ===OBLITERATED===. I'm a fairly calm person but that can be quite frustrating. That wouldn't be eliminated, of course, with more items in the db. However, at least if I do that chasing db info, I know that I am doing so for a reason.

Anyhow, I'm rambling on ten different tangents again, and part of the reason for that is that I don't know what the reasons are for not putting any limited + gear on the db. I can think of only two off the top of my head. 1. Availability: This one is somewhat understandable, though I have some thoughts in that area. 2. "That's what we've always done.": The argument of tradition, which FEELS like (as an outsider) "You have to put the same amount of effort in as the vets have." Which seems an awful lot like "This is how we've always done it." Which is rarely a meritous argument in and of itself.
I would be curious to know what the actual arguments are, since those are more relevant than what I can think of off the top of my head. Then perhaps I would have a better idea of what your expectations are of new players.

TL;DR: Does knowledge of the MM and DMG ruin your experience of that game as a player? Why no limited a on item list (You referenced this as potentially game breaking, how so)? How much time are you expecting a new player should have to put in to playing to be competent as a CF player?