Well I won a Champions Cup among other official cups and if I recall correctly 7 or 8 of my players were homegrown as I was never a big fan of splashing money in the market to buy/sell players, not to mention that usually the USA NT is full of my own homegrown players, I've been slacking a bit this past 3/4 seasons to be honest since I got bored of the game mechanics, lack of SIM updates and recent changes to training & scouting that kind of ruined the enjoyment of the game for me, so my club is on sort of life support mode at the moment waiting for a new SIM or anything that makes the game more fun which hopefully will eventually happen, but overall I'd say I might be doing something right training players if I managed to win multiple cups barely using the transfer market.
These guys get those games from youth leagues already
Obviously my players play the youth leagues, they actually play 4 youth league games a week as most players on U21 also play U23 and they also play friendly games.....
Anyway, that Spencer guy is from when I was paying more attention to training, so he played U18/U21/U23 leagues and 4 friendly games a week, if not more as sometimes I used to sacrifice form so players would gain experience faster so theoretically he should have more experience, he actually played as a starter this whole season and he still is at 8 experience, so I'm sure not all players gain experience at the same rate.
And anyway you missed the main point, and that is that you can't play a 20/21/22/23 y/old on a senior team because of experience, if you play at the top level you shouldn't be playing anyone with less than 9 experience and therefore even if your players get experience at warp speed, a player won't be able to play senior football until he's 25 y/old... which is ridiculous and the cherry on top is that if you have a player with 8 stamina or speed, he's done at 31 y/old... so he's only usable for 6 seasons, he will expend more time training to be a player than actually playing.
If it was up to me, I'd replace experience with a similar but trainable skill, something like "positioning" or whatever you want to call it, it will give you more control over training and overall the manager would have to make the choice about how to train the skill instead of playing endless friendlies... of course you'd have players maxing on the skill as any other skill, so maybe put less weight on it than it currently has.
As a matter of fact, I'd replace "set plays" too... that's a useless skill that could be fun if somehow is replaced with something usable.