I think you might be overthinking this; you only spent a few minutes playing someone else’s bass and it might have just been a neck shape you didn’t care for.
I was able to adjust to a 5-er fairly quickly - and I currently switch back and forth between 5 and 4 without issues but…
…like nickpc, I definitely had to play a few before I found necks that I liked. I’m reasonably tolerant of neck shapes that aren’t my ideal when I play 4-strings but I’m fussier when it comes to 5-ers. I’ve sold several excellent 5-string basses because the necks just didn’t do it for me.
Shop around a little. When you find the neck you like you’ll know it instantly and you’ll find that five strings are no longer a problem.
Similar for me. I was "five curious" for a couple of years before I bought one, and it took awhile before I found a neck I liked. When I ordered a G&L L-1500 in 2006, I considered making it the five-string 1505, but the G&L five-string necks at the time were simply too thick for me, so I held off.
Then, in 2008, Fender slimmed down its five-string necks for the Am. Std. line, and I took the plunge on a Jazz V. I didn't experience much of a transition, and I played it interchangeably with my fours for several years. My fives are now a G&L M-2500--they slimmed down the necks, so I bought one in 2014-- and Sandberg TT-5 Superlight (J5).
Even though I've had fives for many years, I don't think I became a true five-string player until about two years ago. For a long time, I used the B string sparingly, and I still played my fours frequently so I would be able to cover a set on either.
But for the past couple of years, I've been in a Grateful Dead cover band, and all the improvisation has led to a much greater integration of the B string into my playing. I keep finding new opportunities to use it. In that band, it's all fives, all the time, and it would be a major adjustment to play a set on a four. (My other band plays very different material, and if I don't need the B string for anything, I'll use a four. But I usually end up using a five.)
And I think fives magnify the importance of some specs, which makes it more difficult to find one that feels right. Some examples are nut width, string spacing, rear profile, and fretboard radius. Like
@Lo-E, I can be comfortable on lots of fours, but I'm picky about fives. For example, I don't like 19mm spacing at the bridge on fives, but it's standard on many fours, and I'm fine with it.
Fretboard radius is an even bigger deal for me. On fours (and guitars) I like 12" and flatter, but I'm OK with Fender's standard 9.5" radius if the instrument sets up with decently low action. I still love my Strat and Fender J, and I've even liked some fours with vintage 7.5" radius boards.
But on fives? Fuhgetaboutit! I can't stand reaching over a "hump" to access the lower strings, so it's gotta be 12" or flatter. I've had two fives with 9.5" radius fretboards, and they're both gone.