Realization of the Itemization

So in my last game I was and my adc was faced against and . We were doing pretty good in lane, we were actually on par but mostly oppressive on our side since I can easily poke any of them. We kind of actually won lane and was able to rotate to mid lane with a few kills and deaths and at the same time our jgler was also super fed and can easily one shot varus, shaco, and kassadin mid game. Mid to early late game we were strong and almost about to finish, however, in the end we lost and I know two things that majorly lost us:

( Note: I chose to go full ap damage sona, since I thought it helped us so much with getting rid of squishies quickly mid-early late game: shaco, varus, and kassadin. Also I mistakenly forgot to change my mastery to windspeaker, I had stormraiders XD srry :3 )

1. Our yasuo stuck himself up top continuously pushing and 1v5 the enemy team. There was at some point in the game (i think close to end) where we aced them but yasuo and veigar chose to stay in the enemy team base instead of grouping and doing baron. The enemy team had 10 or so seconds left for 2 -3 of them to spawn, but me and rengar could not finish baron that fast and yasuo who was (something-20 deaths and veigar who also had many deaths) aren't strong enough against the enemies that were about to spawn in the enemy base so basically they got pawned. So... in the end they aced us in return and won the game.

2. The enemy team had already built full tank items and LIFESTEAL ITEMS. So going to my point I think the second reason we lost was just the overall sustain our team had, I could not out heal the life steal from enemy team (nunu had his ability to heal himself, varus with the BORK and BT and most of them had spirit visage which aided with sustain).

SUBPOINT (now I know maybe I could have done some things better):

1. I could have built more support items like: Locket, redemption, etc. but then that would mean that our team's potential burst and quickness of getting rid of squishies aforementioned would less likely to be higher and possible. My healing would also be lower but I know that redemption would compensate.
2. Maybe if I also remembered to change my keystone mastery to windspeaker I wouldn't have that issue of having lesser heals with building the support items mentioned.
3. I could have dropped control wards more for vision and shaco.
4. I should have been more insistent of making yasuo and veigar group with us since they were both "feeding" or dying easily for polite purposes.

REALIZATION (now, this is just my own opinion and thinking):

1. Most of the items in league are geared towards helping ad running characters as evidenced by having more variation and overall amount of ad items compared to ap items. It seems that ad items have more variation, valuable stat gains, passives, and utility than ap items. There are so much choice for ad characters to have defensive and sustainable stats but also increasing so much of their ad output: hybrids of attackspeed + lifesteal, attack speed + crit, attack speed + mr, ad + armor, ad + mr and the five most annoying of all are BORK, guardian angel, BT, MAW (with the shield popping off),and DD (1/3 dmg reduction). On the other hand only a few ap items actually give godlike utility, damage, and passive like ad items, my personal faves are: the hextech items (the rocket and ice, gunblade), zhonya, ROA, Liandry's.
2. In connection to the first point, I think that my main and major issue is mainly going towards the topic of LIFESTEAL. The idea that these ad characters who stack up as + dmg + crit + lifesteal can regenerate massive amounts of health per auto just isn't really a good matchup against mages who mainly rely on casting spells and their cooldowns. I mean after casting all your abilities, there isn't really much left. If you are ahead and well fed then maybe you can burst them down real quick but with all these sustain and damage reducing items, late game your burst will almost mean nothing. If you are behind as a mage then I think you're pretty much done and casting your abilities would either just be used for utility like cc or focusing on killing squishy supports.
3. I was really sad when they removed spell vamp item(s). I don't think its unfair to have spell vamp in several ap items since spells have cooldowns anyways and they aren't mana free except maybe for some other ap mages like kat or akali. Autos don't really have cooldowns and they're manaless, and what more? they can be sped up so enemies might as well not really deal any damage to you since you just regenerate endlessly per auto. I get that there's morello and liandry's but come on! only two (I maybe wrong there must be more but as of now these are the only 2 ap Items I can think off) to counter lifesteal?

Suggestion:

1. I would like to see the possibility of giving certain items spell vamp, which items? I really don't know but I think it would be such a great passive and stat gain for mages.

2. Maybe lower the amount of lifesteal % cause they're stacking up attackspeed anyways? and that 1/3 dmg reduction on DD really needs a tweak
3. MORE AP ITEMS PLS if ad's can have GA why can't mages have one that actually gives them ap.

If you are reading this please don't report my english XD Thanks <3