Personally I think team building is an important part of the game, and random pool draft nearly prevents most of it.
Yes, I can see that random gives more chances for weaker champions to shine and encourages improvisation, but sometimes the character combination made the game so one-sided that it's borderline impossible to bring back. Plus competitive mode gives player somewhat chances to counter pick characters and probably improve the meta. If you are concerned about competitive player just spamming "good" characters, just make a ban list, maybe based on community votes since from what I know people tend to agree on what should be banned or what characters are good. Or if you still want to keep random draft as the main arena game mode, I suggest that having more characters(more than 6) or even just simply changing character selecting order(for example a player having the 1st, 4th and 5th pick, the other one have the 2nd, 3rd, 6th pick) could balance the game back more in the first players favor(obviously in random draft since in competitive the first player is the one that have the advantage).
As a conclusion, as a fellow player I would like to have competitive back for the arena game mode, or at least have it alter between both random and competitive. Also as another solution, some rule changes or bans could be applied to make random more balanced and enjoyable.
Hope someone in charge of the rules could read this and just maybe make a little change to make the game more fun!