In my next campaign I'll be exploring the idea of a male drow cleric. We are using the standard array, and that leaves me with a maximum score of 15 in my spellcasting ability, and racial increases to attributes that are not crucial to being a cleric.
Players using optimal races will start with a spellcasting ability score of 17, of course. More spells prepared, higher save DC, better spell attack bonus, et cetera. And possibly a secondary bonus to their Con score for more hit points or other goodies.
Now, I don't want mechanical optimization to trump my roleplaying concept – that means drow and cleric stays, rest is open to changes and adjustments. What can I do to create a drow cleric, but minimize mechanical drawbacks and not be a second class spellcaster?
For a domain, I prefer Light, but it is not set in stone. We start at level 1, and hope to go to 10 or 11.
Tasha’s Cauldron of Everything is forbidden by my DM, as are all materials that came out after it. Variant races and subraces that predate Tasha's are negotiable.
You can't, and it's not that bad.
As you've noted, you aren't playing to optimize while others are. But in the end, that difference is going to be minimal. They will start with a higher modifier by about 1 - which really isn't much of a difference. Your die rolls will much more heavily influence the outcome, minimizing that mechanical issue.
We roll stats at my tables and there can be similar discrepancies in values. My players have not found issue with it, even the ones with 'lower' stats. I have also played characters with lower stats than others at the table and fully enjoyed those characters. I never felt 'behind' because the issue never really came up. We either hit or didn't, got a successful spell off or not.
Not playing an optimized character doesn't at all mean you aren't optimizing for fun.
Are you playing to optimize or aren't you?
You've noted that you don't seem to want to be 'optimizing', but you also ask how to remove some of the things that make your choice suboptimal - which suggests you do care about optimization.
There are things the drow race gives that others don't, and your build optimizes those things rather than the pure mechanical race-class combos can provide. And that's okay!
You don't need to minimize the complications - lean into them. This is your concept, and a concept that isn't fully optimized is more than okay. The bounded accuracy really makes these things not massive, and I've played characters who didn't have optimal mechanics but still were fun. Because the mechanics weren't what made the game fun, but the playing of the characters in the story.
A note on making decisions within the bounds and playstyle differences
We all have different ways of playing the game and we all want to have fun. The decision by the DM to require keeping the options provided and asking players to choose within those bounds is more than okay. It's not "wrong", but it does affect how their players respond - and that's really the issue here.
You should talk to your DM about your build, your concerns, and what can make your character concept come to life in their game. Your reaction is just as reasonable as theirs and nothing is 'wrong' here - it's just a mismatch of styles that can be alleviated by communication.