It sounds like the big issue here is your friends lack of map awareness. Given proper map awareness, a team of 5 on SR can be properly located to catch that 1 player who is out of position. In TT, getting caught out of position is not a big deal because you can get away, therefore less skill is needed to properly position your self.
As far as skill in debating goes, it seems like your friend is lacking in skill. far too much exaggeration, as well as a lack of explination as to why potions are inherently bad. Truthfully, in SR, no one is required to take potions, but they do so that they can remain in lane longer and gain xp, so that if their enemies do not have potions they must lose out on that experience. However, this xp loss can be made up for during the course of the game, which prevents snowballing from early xp loss or deaths from ganks.
Ultimately it sound like your friend is qqing about losing so much. Lets look at the three lame things that happen:
1) People stay in lane, causing the game to take longer. This can be resolved multiple ways. your friend is a person too, he can LEAVE his lane to gank lanes that are over extended, so he can resolve this by himself. Another way is he can either learn to jungle, or level up to a point where someone will jungle on the team. This will allow for someone to always be out of lane and ganking.
2) I get ganked by the whole enemy team. When the entire enemy team is missing, it is not a good time to push your lane. chances are they are getting dragon and then they will kill you for being over-extended, communicate with your team and this will not be an issue. furthermore wards (map awareness) will let you know when a gank is comming. this is not as necessary in TT because everyone is in lane, as junglers are uncommon so when someone is missing and did not have no health, they are coming for a gank. Heaven forbid that there should be more strategy involved.
3) All that must be done in team fights is spam skills. This is exactly why your friend doesn't like SR. Clearly the strategy of focusing the carry escapes him. simply spamming skills will do some damage to each person on the enemy team, but won't kill any of them. In the mean time, the enemy kills your [ranged] ad carry, ap carry and support, thus removing the majority of the damage on your team, followed by your melee ad and then tank. they are all hurt, but your team is dead, no worries, they have time to push and the go back to heal.
So really to be sucessful in SR, one must not only have the 'individual skill' to win their lane, but the communication skills to help other lanes and the positioning and map awareness skills to prevent setting themself up for a gank, but also to successfully gank other lanes in order to win.